When I want to go in the nether, I got logged out. And get this message '---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 20-9-13 17:16
Description: Exception generating new chunk

java.lang.NullPointerException
at agj.b(SourceFile:170)
at agj.d(SourceFile:200)
at km.c(SourceFile:72)
at km.d(SourceFile:104)
at ade.e(SourceFile:293)
at ade.a(SourceFile:233)
at ads.b(SourceFile:85)
at ads.a(SourceFile:50)
at jh.a(SourceFile:438)
at jh.a(SourceFile:368)
at kq.b(SourceFile:353)
at om.B(SourceFile:321)
at pe.B(SourceFile:165)
at om.h(SourceFile:284)
at pe.h(SourceFile:1159)
at vg.h(SourceFile:205)
at kq.i(SourceFile:198)
at kv.a(SourceFile:196)
at gn.a(SourceFile:136)
at eb.b(SourceFile:63)
at kv.e(SourceFile:64)
at ky.b(SourceFile:37)
at bow.b(SourceFile:83)
at net.minecraft.server.MinecraftServer.u(SourceFile:487)
at net.minecraft.server.MinecraftServer.t(SourceFile:404)
at bot.t(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:338)
at jc.run(SourceFile:581)

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

– Head –
Stacktrace:
at agj.b(SourceFile:170)
at agj.d(SourceFile:200)

– Chunk to be generated –
Details:
Location: -6,6
Position hash: 30064771066
Generator: HellRandomLevelSource
Stacktrace:
at km.c(SourceFile:72)
at km.d(SourceFile:104)
at ade.e(SourceFile:293)

– Requested block coordinates –
Details:
Found chunk: true
Location: World: (-96,127,96), Chunk: (at 0,7,0 in -6,6; contains blocks -96,0,96 to -81,255,111), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Stacktrace:
at ade.a(SourceFile:233)
at ads.b(SourceFile:85)
at ads.a(SourceFile:50)
at jh.a(SourceFile:438)
at jh.a(SourceFile:368)
at kq.b(SourceFile:353)
at om.B(SourceFile:321)
at pe.B(SourceFile:165)
at om.h(SourceFile:284)
at pe.h(SourceFile:1159)
at vg.h(SourceFile:205)

– Player being ticked –
Details:
Entity Type: null (kq)
Entity ID: 208
Entity Name: arendgb
Entity's Exact location: -21,00, 84,00, 39,00
Entity's Block location: World: (-21,84,39), Chunk: (at 11,5,7 in -2,2; contains blocks -32,0,32 to -17,255,47), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Entity's Momentum: 0,00, -0,08, 0,00
Stacktrace:
at kq.i(SourceFile:198)
at kv.a(SourceFile:196)
at gn.a(SourceFile:136)
at eb.b(SourceFile:63)
at kv.e(SourceFile:64)

– Ticking connection –
Details:
Connection: kv@4b2235b4
Stacktrace:
at ky.b(SourceFile:37)
at bow.b(SourceFile:83)
at net.minecraft.server.MinecraftServer.u(SourceFile:487)
at net.minecraft.server.MinecraftServer.t(SourceFile:404)
at bot.t(SourceFile:124)
at net.minecraft.server.MinecraftServer.run(SourceFile:338)
at jc.run(SourceFile:581)

– System Details –
Details:
Minecraft Version: 13w38b
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.7.0_10, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 149928664 bytes (142 MB) / 280035328 bytes (267 MB) up to 954466304 bytes (910 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
AABB Pool Size: 4748 (265888 bytes; 0 MB) allocated, 4587 (256872 bytes; 0 MB) used
IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1271 (71176 bytes; 0 MB) allocated, 1035 (57960 bytes; 0 MB) used
Player Count: 1 / 8; [kq['arendgb'/208, l='New World', x=-21,00, y=84,00, z=39,00]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.'