Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at kd.g(SourceFile:226)
	at kd.b(SourceFile:134)

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 7.9.2013 0:32
Description: Exception ticking world

java.lang.NullPointerException
	at kd.g(SourceFile:226)
	at kd.b(SourceFile:134)
	at net.minecraft.server.MinecraftServer.t(SourceFile:455)
	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 kd.g(SourceFile:226)
	at kd.b(SourceFile:134)

-- Affected level --
Details:
	Level name: 13w36a
	All players: 1 total; [kg['tayttapaskaa'/285, l='13w36a', x=-11155,55, y=63,00, z=2358,70]]
	Chunk stats: ServerChunkCache: 1069 Drop: 0
	Level seed: 5916697374028683210
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options: 
	Level spawn location: World: (76,64,196), Chunk: (at 12,4,4 in 4,12; contains blocks 64,0,192 to 79,255,207), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 175320 game time, 117159 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 667 (now: false), thunder time: 68886 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: true
Stacktrace:
	at net.minecraft.server.MinecraftServer.t(SourceFile:455)
	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_11, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 306782520 bytes (292 MB) / 493092864 bytes (470 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 5803 (324968 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	IntCache: cache: 1, tcache: 1, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 14748 (825888 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Player Count: 1 / 8; [kg['tayttapaskaa'/285, l='13w36a', x=-11155,55, y=63,00, z=2358,70]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.