A villager had spawned that gave nothing in exchange for 6 fish and an emerald. Upon trading with said villager, the game crashes. I've included the crash report below.

---- Minecraft Crash Report ----
// Why did you do that?

Time: 1/25/14 5:12 PM
Description: Updating screen events

java.lang.NullPointerException: Updating screen events
at abe.j(SourceFile:158)
at abe.a(SourceFile:87)
at abk.c(SourceFile:81)
at aac.a(SourceFile:237)
at bmv.a(SourceFile:338)
at bgh.a(SourceFile:513)
at bgh.b(SourceFile:484)
at bfc.d(SourceFile:248)
at bfc.k(SourceFile:219)
at bby.p(SourceFile:1352)
at bby.aj(SourceFile:774)
at bby.f(SourceFile:728)
at net.minecraft.client.main.Main.main(SourceFile:154)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at abe.j(SourceFile:158)
at abe.a(SourceFile:87)
at abk.c(SourceFile:81)
at aac.a(SourceFile:237)
at bmv.a(SourceFile:338)
at bgh.a(SourceFile:513)
at bgh.b(SourceFile:484)
at bfc.d(SourceFile:248)
at bfc.k(SourceFile:219)

– Affected screen –
Details:
Screen name: bhg

– Affected level –
Details:
Level name: MpServer
All players: 1 total; [boy['burningstar12'/307, l='MpServer', x=-1880.20, y=7.78, z=1028.77]]
Chunk stats: MultiplayerChunkCache: 169, 169
Level seed: 0
Level generator: ID 01 - flat, ver 0. Features enabled: false
Level generator options:
Level spawn location: -2072.00,4.00,958.00 - World: (-2072,4,958), Chunk: (at 8,0,14 in -130,59; contains blocks -2080,0,944 to -2065,255,959), Region: (-5,1; contains chunks -160,32 to -129,63, blocks -2560,0,512 to -2049,255,1023)
Level time: 146255 game time, 35714 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: true), thunder time: 0 (now: false)
Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
Forced entities: 197 total; [xj['item.item.string'/2341575, l='MpServer', x=-1884.47, y=4.13, z=1005.22], xj['item.item.string'/2059139, l='MpServer', x=-1867.66, y=4.13, z=1028.34], xj['item.item.string'/2369088, l='MpServer', x=-1883.13, y=4.13, z=1007.59], xj['item.item.string'/2026733, l='MpServer', x=-1884.28, y=4.13, z=1028.31], xj['item.item.arrow'/2305705, l='MpServer', x=-1884.97, y=4.13, z=998.69], xj['item.item.bone'/2305707, l='MpServer', x=-1883.78, y=4.13, z=999.88], xj['item.item.rottenFlesh'/2467189, l='MpServer', x=-1887.69, y=4.13, z=1014.28], xj['item.item.rottenFlesh'/2458931, l='MpServer', x=-1890.88, y=4.13, z=1006.63], xj['item.item.rottenFlesh'/2464499, l='MpServer', x=-1894.00, y=4.13, z=1011.59], xj['item.item.slimeball'/2637886, l='MpServer', x=-1820.16, y=4.13, z=966.03], xj['item.item.arrow'/2330597, l='MpServer', x=-1898.34, y=4.13, z=1005.69], yr['Zombie'/2396747, l='MpServer', x=-1897.69, y=5.00, z=1046.84], xj['item.item.bone'/2262393, l='MpServer', x=-1879.09, y=4.13, z=1010.00], xj['item.item.rottenFlesh'/2611809, l='MpServer', x=-1884.22, y=4.13, z=1041.19], xj['item.item.bone'/2288475, l='MpServer', x=-1898.69, y=4.13, z=1018.63], xj['item.item.rottenFlesh'/2619118, l='MpServer', x=-1885.72, y=4.13, z=1040.25], xj['item.item.arrow'/2288474, l='MpServer', x=-1897.09, y=4.13, z=1017.16], xj['item.item.string'/2109805, l='MpServer', x=-1880.53, y=5.13, z=1029.78], xj['item.item.slimeball'/2808056, l='MpServer', x=-1829.31, y=4.13, z=966.97], xj['item.item.slimeball'/2808057, l='MpServer', x=-1826.97, y=4.13, z=966.75], xj['item.item.rottenFlesh'/2653662, l='MpServer', x=-1875.09, y=4.13, z=1042.75], xj['item.item.bone'/2407560, l='MpServer', x=-1886.94, y=4.13, z=1004.34], xz['Cave Spider'/2338861, l='MpServer', x=-1901.69, y=4.00, z=1002.00], xj['item.item.string'/1750487, l='MpServer', x=-1871.22, y=4.13, z=1024.22], xj['item.item.string'/2370253, l='MpServer', x=-1885.75, y=4.13, z=1007.50], xj['item.item.arrow'/2271072, l='MpServer', x=-1887.22, y=4.13, z=1008.78], xj['item.item.string'/2370254, l='MpServer', x=-1885.59, y=4.13, z=1009.50], xj['item.item.bone'/2271073, l='MpServer', x=-1889.13, y=4.13, z=1009.19], xj['item.item.string'/2030020, l='MpServer', x=-1880.84, y=4.13, z=1028.16], xj['item.item.arrow'/2261318, l='MpServer', x=-1882.16, y=4.13, z=1010.38], xj['item.item.slimeball'/2590043, l='MpServer', x=-1843.41, y=4.13, z=1005.06], xj['item.item.string'/2346792, l='MpServer', x=-1883.06, y=4.13, z=1011.50], xj['item.item.bone'/2261319, l='MpServer', x=-1881.41, y=4.13, z=1011.81], xj['item.item.arrow'/2407558, l='MpServer', x=-1886.75, y=4.13, z=1004.53], xj['item.item.string'/2030019, l='MpServer', x=-1880.25, y=4.13, z=1028.88], xj['item.item.bone'/2269979, l='MpServer', x=-1890.00, y=4.13, z=1004.56], xj['item.item.arrow'/2269978, l='MpServer', x=-1889.59, y=4.13, z=1005.75], xj['item.tile.flower2.poppy'/2262326, l='MpServer', x=-1883.00, y=4.13, z=1009.28], xj['item.item.slimeball'/2637890, l='MpServer', x=-1930.06, y=4.13, z=973.16], xj['item.item.arrow'/2267359, l='MpServer', x=-1890.75, y=4.13, z=1009.81], xj['item.item.slimeball'/2637888, l='MpServer', x=-1929.19, y=4.13, z=971.22], xj['item.item.slimeball'/2081884, l='MpServer', x=-1854.81, y=4.13, z=998.28], xj['item.item.arrow'/2344803, l='MpServer', x=-1898.97, y=4.13, z=1012.28], xj['item.item.arrow'/2268273, l='MpServer', x=-1886.34, y=4.13, z=1009.13], xj['item.item.arrow'/2289036, l='MpServer', x=-1870.75, y=4.13, z=1006.38], xj['item.item.bone'/2289038, l='MpServer', x=-1870.81, y=4.13, z=1006.72], yr['Zombie'/2420679, l='MpServer', x=-1897.50, y=5.00, z=1046.31], xj['item.item.slimeball'/2819684, l='MpServer', x=-1848.16, y=4.13, z=993.94], xj['item.item.string'/2046085, l='MpServer', x=-1871.19, y=4.13, z=1027.72], xj['item.item.slimeball'/2433672, l='MpServer', x=-1817.56, y=4.13, z=1057.75], xj['item.item.slimeball'/2726038, l='MpServer', x=-1835.84, y=4.13, z=974.78], xj['item.item.slimeball'/2433669, l='MpServer', x=-1821.06, y=4.13, z=1056.56], xj['item.item.slimeball'/2726036, l='MpServer', x=-1832.03, y=4.13, z=971.09], xj['item.item.slimeball'/2726034, l='MpServer', x=-1834.84, y=4.13, z=971.50], xj['item.item.string'/2141010, l='MpServer', x=-1883.91, y=4.13, z=1018.19], xj['item.item.slimeball'/2433667, l='MpServer', x=-1822.63, y=4.13, z=1057.19], xj['item.item.string'/2137686, l='MpServer', x=-1878.34, y=4.13, z=1012.09], xj['item.item.string'/2344775, l='MpServer', x=-1886.56, y=4.13, z=1008.28], xj['item.item.string'/2108019, l='MpServer', x=-1884.91, y=4.13, z=1017.13], xj['item.item.rottenFlesh'/2464806, l='MpServer', x=-1888.19, y=4.13, z=1017.50], ya['Creeper'/2299333, l='MpServer', x=-1888.94, y=5.00, z=1051.44], xj['item.item.string'/2067602, l='MpServer', x=-1876.72, y=4.13, z=1032.97], xj['item.item.arrow'/2262994, l='MpServer', x=-1878.16, y=4.13, z=1010.81], xj['item.item.slimeball'/2907922, l='MpServer', x=-1842.69, y=4.13, z=995.81], xj['item.item.bone'/2346953, l='MpServer', x=-1886.84, y=4.13, z=1007.84], yn['Slime'/2928082, l='MpServer', x=-1819.60, y=4.00, z=1066.40], xj['item.item.slimeball'/1047057, l='MpServer', x=-1846.81, y=4.13, z=995.78], xj['item.item.rottenFlesh'/2551764, l='MpServer', x=-1885.97, y=4.13, z=1034.28], xj['item.item.slimeball'/1898761, l='MpServer', x=-1832.19, y=4.13, z=973.09], xz['Cave Spider'/2339563, l='MpServer', x=-1870.47, y=4.00, z=1015.83], xj['item.item.rottenFlesh'/2672054, l='MpServer', x=-1882.75, y=4.13, z=1045.84], xj['item.item.arrow'/2344745, l='MpServer', x=-1886.91, y=4.13, z=1010.16], xj['item.item.bone'/2344746, l='MpServer', x=-1887.56, y=4.13, z=1011.22], xj['item.item.slimeball'/2230336, l='MpServer', x=-1925.97, y=4.13, z=969.25], xj['item.item.slimeball'/2230337, l='MpServer', x=-1923.66, y=4.13, z=970.16], xj['item.item.arrow'/2343263, l='MpServer', x=-1896.06, y=4.13, z=1008.19], xj['item.item.rottenFlesh'/2612945, l='MpServer', x=-1884.88, y=4.13, z=1044.69], yw['Villager'/236, l='MpServer', x=-1891.51, y=4.63, z=1029.50], xj['item.item.rottenFlesh'/2689223, l='MpServer', x=-1876.44, y=4.13, z=1028.22], yw['Villager'/235, l='MpServer', x=-1914.31, y=5.00, z=1035.44], ws['Iron Golem'/234, l='MpServer', x=-1876.47, y=4.00, z=1043.72], xj['item.item.slimeball'/2754810, l='MpServer', x=-1843.53, y=4.13, z=997.59], xj['item.item.slimeball'/2754815, l='MpServer', x=-1842.78, y=4.13, z=992.19], xj['item.item.bone'/2343265, l='MpServer', x=-1895.91, y=4.13, z=1007.84], xj['item.item.arrow'/2343264, l='MpServer', x=-1895.66, y=4.13, z=1006.84], xj['item.item.slimeball'/2754812, l='MpServer', x=-1843.63, y=4.13, z=1000.94], ym['Skeleton'/1319419, l='MpServer', x=-1865.50, y=9.00, z=1026.50], xj['item.item.slimeball'/2537142, l='MpServer', x=-1885.63, y=4.13, z=1003.75], xj['item.item.seeds'/2149374, l='MpServer', x=-1866.16, y=5.13, z=1033.25], xj['item.item.wheat'/2149372, l='MpServer', x=-1865.81, y=5.13, z=1034.53], xj['item.item.seeds'/2149373, l='MpServer', x=-1865.13, y=5.13, z=1035.28], yw['Villager'/279, l='MpServer', x=-1880.28, y=5.00, z=1027.56], xj['item.item.rottenFlesh'/2627307, l='MpServer', x=-1883.13, y=4.13, z=1046.94], yw['Villager'/282, l='MpServer', x=-1906.66, y=4.00, z=1030.72], yw['Villager'/281, l='MpServer', x=-1892.13, y=4.00, z=1035.50], xj['item.item.bone'/2283832, l='MpServer', x=-1879.28, y=4.13, z=1012.00], ws['Iron Golem'/263, l='MpServer', x=-1888.42, y=4.00, z=1045.00], yw['Villager'/267, l='MpServer', x=-1894.57, y=4.00, z=1026.99], yw['Villager'/271, l='MpServer', x=-1902.50, y=4.00, z=1029.78], xj['item.item.rottenFlesh'/2631609, l='MpServer', x=-1879.97, y=4.13, z=1042.94], xj['item.item.rottenFlesh'/2683252, l='MpServer', x=-1873.59, y=4.13, z=1028.34], xj['item.item.slimeball'/2488266, l='MpServer', x=-1841.56, y=4.13, z=968.63], xj['item.item.string'/1943505, l='MpServer', x=-1875.16, y=4.13, z=1032.16], xj['item.item.slimeball'/2494346, l='MpServer', x=-1821.84, y=4.13, z=1067.75], xj['item.item.rottenFlesh'/2673862, l='MpServer', x=-1880.25, y=4.13, z=1046.47], xj['item.item.arrow'/2267542, l='MpServer', x=-1880.84, y=4.13, z=1010.25], ws['Iron Golem'/292, l='MpServer', x=-1878.57, y=4.00, z=1028.30], xj['item.item.slimeball'/2194968, l='MpServer', x=-1814.44, y=4.13, z=1063.06], xj['item.item.slimeball'/2194965, l='MpServer', x=-1816.06, y=4.13, z=1061.19], xj['item.item.slimeball'/2376131, l='MpServer', x=-1816.38, y=4.13, z=1062.34], xj['item.item.arrow'/2460411, l='MpServer', x=-1910.16, y=4.13, z=1017.06], xj['item.item.arrow'/2281864, l='MpServer', x=-1883.13, y=4.13, z=1011.78], xj['item.item.slimeball'/2376133, l='MpServer', x=-1814.75, y=4.13, z=1057.69], ws['Iron Golem'/300, l='MpServer', x=-1877.81, y=4.00, z=1038.72], yw['Villager'/301, l='MpServer', x=-1879.56, y=4.69, z=1029.57], xj['item.item.string'/2066720, l='MpServer', x=-1873.19, y=4.13, z=1031.44], xj['item.item.arrow'/2279515, l='MpServer', x=-1887.84, y=4.13, z=1010.75], xj['item.item.string'/2014758, l='MpServer', x=-1883.94, y=4.13, z=1025.53], xj['item.item.slimeball'/2673824, l='MpServer', x=-1931.00, y=4.13, z=978.56], xj['item.item.slimeball'/2673825, l='MpServer', x=-1887.94, y=4.13, z=1005.91], xj['item.item.slimeball'/2104450, l='MpServer', x=-1838.38, y=4.13, z=972.47], xj['item.item.string'/2461983, l='MpServer', x=-1892.06, y=4.13, z=1014.88], xj['item.item.slimeball'/2104449, l='MpServer', x=-1841.16, y=4.13, z=977.09], xj['item.item.arrow'/2279489, l='MpServer', x=-1875.56, y=4.13, z=1006.53], xj['item.item.string'/1707546, l='MpServer', x=-1873.31, y=4.13, z=1027.06], xj['item.item.slimeball'/2548909, l='MpServer', x=-1882.81, y=4.13, z=999.34], xj['item.item.slimeball'/2548910, l='MpServer', x=-1879.75, y=4.13, z=999.69], xj['item.item.spiderEye'/2112157, l='MpServer', x=-1886.75, y=4.13, z=1022.97], xj['item.item.string'/2345066, l='MpServer', x=-1887.31, y=4.13, z=1010.28], xj['item.item.string'/2112156, l='MpServer', x=-1887.03, y=4.13, z=1022.91], xj['item.item.slimeball'/2209614, l='MpServer', x=-1886.56, y=4.13, z=1089.97], sm['Experience Orb'/2110563, l='MpServer', x=-1881.25, y=4.25, z=1028.80], sm['Experience Orb'/2110562, l='MpServer', x=-1880.01, y=7.77, z=1028.41], sm['Experience Orb'/2110561, l='MpServer', x=-1880.62, y=4.25, z=1028.72], xj['item.item.slimeball'/2673822, l='MpServer', x=-1926.09, y=4.13, z=974.75], sm['Experience Orb'/2108878, l='MpServer', x=-1881.25, y=4.25, z=1028.93], xj['item.item.slimeball'/2673821, l='MpServer', x=-1928.31, y=4.13, z=974.63], sm['Experience Orb'/2108876, l='MpServer', x=-1881.25, y=4.25, z=1028.91], xj['item.item.slimeball'/2578453, l='MpServer', x=-1849.78, y=4.13, z=998.78], xj['item.item.bone'/2268573, l='MpServer', x=-1880.16, y=4.13, z=1008.50], xj['item.item.slimeball'/1213311, l='MpServer', x=-1813.75, y=4.13, z=1066.56], xj['item.item.rottenFlesh'/2461191, l='MpServer', x=-1886.84, y=4.13, z=1003.88], xj['item.item.arrow'/2267098, l='MpServer', x=-1880.38, y=4.13, z=1009.03], xj['item.item.string'/2112126, l='MpServer', x=-1885.94, y=4.13, z=1021.06], xj['item.item.string'/1970497, l='MpServer', x=-1883.25, y=4.13, z=1024.81], xj['item.item.slimeball'/2257487, l='MpServer', x=-1813.22, y=4.13, z=1062.09], xj['item.item.slimeball'/2257485, l='MpServer', x=-1816.75, y=4.13, z=1054.59], xj['item.item.rottenFlesh'/2673159, l='MpServer', x=-1881.06, y=4.13, z=1044.38], xj['item.item.slimeball'/2662514, l='MpServer', x=-1843.03, y=4.13, z=973.22], xj['item.item.slimeball'/2662515, l='MpServer', x=-1837.81, y=4.13, z=975.31], xj['item.item.slimeball'/2257489, l='MpServer', x=-1817.97, y=4.13, z=1060.84], xj['item.item.slimeball'/2662518, l='MpServer', x=-1838.94, y=4.13, z=977.91], xj['item.item.slimeball'/2662519, l='MpServer', x=-1841.13, y=4.13, z=979.94], xj['item.item.rottenFlesh'/2466433, l='MpServer', x=-1885.72, y=4.13, z=1015.75], xj['item.item.string'/2341228, l='MpServer', x=-1888.09, y=4.13, z=1005.31], xj['item.item.slimeball'/2662517, l='MpServer', x=-1843.19, y=4.13, z=976.22], xj['item.item.rottenFlesh'/2662522, l='MpServer', x=-1883.63, y=4.13, z=1037.38], xj['item.item.string'/2080494, l='MpServer', x=-1871.72, y=4.13, z=1035.47], xj['item.item.rottenFlesh'/2660777, l='MpServer', x=-1876.56, y=4.13, z=1032.84], xj['item.item.arrow'/2284463, l='MpServer', x=-1876.78, y=4.13, z=1009.09], xj['item.item.string'/2107726, l='MpServer', x=-1886.97, y=4.13, z=1017.25], xj['item.item.arrow'/2268494, l='MpServer', x=-1880.25, y=4.13, z=1011.50], xj['item.item.rottenFlesh'/2630937, l='MpServer', x=-1880.19, y=4.13, z=1045.59], xj['item.item.slimeball'/2626071, l='MpServer', x=-1825.94, y=4.13, z=976.06], xj['item.item.slimeball'/2626069, l='MpServer', x=-1821.53, y=4.13, z=972.41], xj['item.item.slimeball'/2626068, l='MpServer', x=-1823.59, y=4.13, z=972.22], xj['item.item.arrow'/2284000, l='MpServer', x=-1874.09, y=4.13, z=1014.22], xj['item.item.rottenFlesh'/2467006, l='MpServer', x=-1891.69, y=4.13, z=1010.53], xj['item.item.bone'/2284001, l='MpServer', x=-1873.72, y=4.13, z=1013.53], xj['item.item.seeds'/2262152, l='MpServer', x=-1869.81, y=5.13, z=1032.44], xj['item.item.string'/1776079, l='MpServer', x=-1870.81, y=4.13, z=1020.72], xj['item.item.slimeball'/2502436, l='MpServer', x=-1873.69, y=4.13, z=1002.00], xj['item.item.wheat'/2262151, l='MpServer', x=-1870.56, y=5.13, z=1031.38], xj['item.item.string'/2343542, l='MpServer', x=-1892.72, y=4.13, z=1010.75], xj['item.item.string'/2025851, l='MpServer', x=-1873.38, y=4.13, z=1015.72], xz['Cave Spider'/2334852, l='MpServer', x=-1864.31, y=4.00, z=1010.53], xj['item.item.slimeball'/2697645, l='MpServer', x=-1846.91, y=4.13, z=1003.25], xj['item.item.slimeball'/2837345, l='MpServer', x=-1842.63, y=4.13, z=994.78], xj['item.item.slimeball'/2697647, l='MpServer', x=-1851.81, y=4.13, z=1006.41], xj['item.item.slimeball'/2837347, l='MpServer', x=-1847.94, y=4.13, z=1000.91], xj['item.item.slimeball'/2837348, l='MpServer', x=-1846.78, y=4.13, z=999.75], xj['item.item.slimeball'/2795650, l='MpServer', x=-1878.13, y=4.13, z=1000.84], xj['item.item.slimeball'/2697641, l='MpServer', x=-1854.53, y=4.13, z=1003.94], xj['item.item.slimeball'/2697643, l='MpServer', x=-1852.44, y=4.13, z=1003.81], xj['item.item.spiderEye'/2256897, l='MpServer', x=-1861.84, y=4.13, z=1003.47], xj['item.item.slimeball'/2837343, l='MpServer', x=-1841.09, y=4.13, z=995.09], xj['item.item.slimeball'/2837341, l='MpServer', x=-1844.19, y=4.13, z=995.44], xj['item.item.rottenFlesh'/2468461, l='MpServer', x=-1892.88, y=4.13, z=1008.56], xj['item.item.slimeball'/2837340, l='MpServer', x=-1846.53, y=4.13, z=992.16], boy['burningstar12'/307, l='MpServer', x=-1880.20, y=7.78, z=1028.77], xj['item.item.slimeball'/2825373, l='MpServer', x=-1829.97, y=4.13, z=976.88], xj['item.item.slimeball'/2825372, l='MpServer', x=-1826.88, y=4.13, z=973.59], sm['Experience Orb'/2257457, l='MpServer', x=-1862.22, y=4.25, z=1000.25], sm['Experience Orb'/2257458, l='MpServer', x=-1861.91, y=4.25, z=1002.66], xj['item.item.slimeball'/2825370, l='MpServer', x=-1829.69, y=4.13, z=972.94], sm['Experience Orb'/2257459, l='MpServer', x=-1859.50, y=4.25, z=1006.94], xj['item.item.arrow'/2347893, l='MpServer', x=-1884.19, y=4.13, z=1014.63]]
Retry entities: 0 total; []
Server brand: vanilla
Server type: Integrated singleplayer server
Stacktrace:
at bmw.a(SourceFile:298)
at bby.b(SourceFile:2029)
at bby.f(SourceFile:737)
at net.minecraft.client.main.Main.main(SourceFile:154)

– System Details –
Details:
Minecraft Version: 14w04b
Operating System: Windows 8 (x86) version 6.2
Java Version: 1.7.0_45, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode), Oracle Corporation
Memory: 24489368 bytes (23 MB) / 146395136 bytes (139 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 14w04b
LWJGL: 2.9.1
OpenGL: AMD Radeon HD 7800 Series GL version 4.3.12618 Compatibility Profile Context 13.251.0.0, ATI Technologies Inc.
GL Caps: Using GL 1.3 multitexturing.
Using framebuffer objects because OpenGL 3.0 is supported and separate blending is supported.
Anisotropic filtering is supported and maximum anisotropy is 16.
Shaders are available because OpenGL 2.1 is supported.

Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: []
Current Language: English (US)
Profiler Position: N/A (disabled)
Anisotropic Filtering: Off (1)