A detailed walkthrough of the error, its code path and all known details is as follows:
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– Head –
Stacktrace:
at ayv.f(SourceFile:263)
at are.b(SourceFile:123)
at are.a(SourceFile:59)
at sp.a(SourceFile:514)
at wx.c(SourceFile:1749)
at adx.c(SourceFile:312)
at wx.K(SourceFile:303)
at wx.t_(SourceFile:266)
at adx.t_(SourceFile:77)
at aqr.a(SourceFile:1407)
at qu.a(SourceFile:600)
at aqr.g(SourceFile:1385)

– Entity being ticked –
Details:
Entity Type: Item (adx)
Entity ID: 10118
Entity Name: item.tile.flower2.poppy
Entity's Exact location: -9.00, 70.52, 8.00
Entity's Block location: -9.00,70.00,8.00 - World: (-9,70,8), Chunk: (at 7,4,8 in -1,0; contains blocks -16,0,0 to -1,255,15), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Entity's Momentum: 0.20, 0.18, 0.06
Entity's Rider: ~_ERROR~ NullPointerException: null
Entity's Vehicle: ~_ERROR~ NullPointerException: null
Stacktrace:
at aqr.i(SourceFile:1278)
at qu.i(SourceFile:478)

– Affected level –
Details:
x=-79.11, y=68.00, z=59.61]]
Chunk stats: ServerChunkCache: 725 Drop: 0
Level seed: 881045815
Level generator: ID 00 - default, ver 1. Features enabled: true
Level generator options:
Level spawn location: -76.00,64.00,72.00 - World: (-76,64,72), Chunk: (at 4,4,8 in -5,4; contains blocks -80,0,64 to -65,255,79), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 2329403 game time, 2329403 day time
Level dimension: 0
Level storage version: 0x04ABD - Anvil
Level weather: Rain time: 47222 (now: false), thunder time: 23832 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.A(SourceFile:608)
at net.minecraft.server.MinecraftServer.z(SourceFile:532)
at cyk.z(SourceFile:155)
at net.minecraft.server.MinecraftServer.run(SourceFile:448)
at java.lang.Thread.run(Thread.java:745)

– System Details –
Details:
Minecraft Version: 1.8.1
Operating System: Windows 8.1 (amd64) version 6.3
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 449981776 bytes (429 MB) / 833269760 bytes (794 MB) up to 4241293312 bytes (4044 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx4G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn512M
IntCache: cache: 5, tcache: 41, allocated: 13, tallocated: 95
Profiler Position: N/A (disabled)
x=-79.11, y=68.00, z=59.61]]
Type: Integrated Server (map_client.txt)
Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.