Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at ny.a(SourceFile:89)
	at ou.aL(SourceFile:396)
	at ou.z(SourceFile:222)
	at ov.z(SourceFile:128)
	at oc.o_(SourceFile:279)
	at ou.o_(SourceFile:1167)
	at ov.o_(SourceFile:169)
	at uj.o_(SourceFile:81)
	at act.a(SourceFile:1365)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)

---- Minecraft Crash Report ----
// Sorry :(

Time: 6-9-13 20:51
Description: Ticking entity

java.lang.NullPointerException
	at ny.a(SourceFile:89)
	at ou.aL(SourceFile:396)
	at ou.z(SourceFile:222)
	at ov.z(SourceFile:128)
	at oc.o_(SourceFile:279)
	at ou.o_(SourceFile:1167)
	at ov.o_(SourceFile:169)
	at uj.o_(SourceFile:81)
	at act.a(SourceFile:1365)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)
	at act.h(SourceFile:1250)
	at kd.h(SourceFile:364)
	at net.minecraft.server.MinecraftServer.t(SourceFile:463)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bnn.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hr.run(SourceFile:575)


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

-- Head --
Stacktrace:
	at ny.a(SourceFile:89)
	at ou.aL(SourceFile:396)
	at ou.z(SourceFile:222)
	at ov.z(SourceFile:128)
	at oc.o_(SourceFile:279)
	at ou.o_(SourceFile:1167)
	at ov.o_(SourceFile:169)
	at uj.o_(SourceFile:81)
	at act.a(SourceFile:1365)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)

-- Entity being ticked --
Details:
	Entity Type: Slime (uj)
	Entity ID: 145787
	Entity Name: Slime
	Entity's Exact location: -869,50, 57,00, 350,50
	Entity's Block location: World: (-870,57,350), Chunk: (at 10,3,14 in -55,21; contains blocks -880,0,336 to -865,255,351), Region: (-2,0; contains chunks -64,0 to -33,31, blocks -1024,0,0 to -513,255,511)
	Entity's Momentum: 0,00, 0,00, 0,00
Stacktrace:
	at act.h(SourceFile:1250)
	at kd.h(SourceFile:364)

-- Affected level --
Details:
	Level name: New World
	All players: 1 total; [kg['darth_naber'/127256, l='New World', x=-871,18, y=56,00, z=349,48]]
	Chunk stats: ServerChunkCache: 561 Drop: 0
	Level seed: -2134467534690167878
	Level generator: ID 01 - flat, ver 0. Features enabled: true
	Level generator options: 2;7,3x1,52x24;2;
	Level spawn location: World: (-869,4,367), Chunk: (at 11,0,15 in -55,22; contains blocks -880,0,352 to -865,255,367), Region: (-2,0; contains chunks -64,0 to -33,31, blocks -1024,0,0 to -513,255,511)
	Level time: 8859 game time, 8859 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 16214 (now: false), thunder time: 158280 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.t(SourceFile:463)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bnn.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hr.run(SourceFile:575)

-- System Details --
Details:
	Minecraft Version: 13w36b
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 408126160 bytes (389 MB) / 1072693248 bytes (1023 MB) up to 1908932608 bytes (1820 MB)
	JVM Flags: 3 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xms1g -Xmx2g
	AABB Pool Size: 517 (28952 bytes; 0 MB) allocated, 453 (25368 bytes; 0 MB) used
	IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 71 (3976 bytes; 0 MB) allocated, 42 (2352 bytes; 0 MB) used
	Player Count: 1 / 8; [kg['darth_naber'/127256, l='New World', x=-871,18, y=56,00, z=349,48]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.