Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at ou.a(SourceFile:523)
	at kg.a(SourceFile:677)
	at ou.c(SourceFile:493)
	at zj.b(SourceFile:79)
	at yx.b(SourceFile:116)
	at uw.o(SourceFile:294)
	at kg.o(SourceFile:654)
	at uw.o_(SourceFile:175)

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

Time: 2013-09-06 17:21
Description: Ticking player

java.lang.NullPointerException
	at ou.a(SourceFile:523)
	at kg.a(SourceFile:677)
	at ou.c(SourceFile:493)
	at zj.b(SourceFile:79)
	at yx.b(SourceFile:116)
	at uw.o(SourceFile:294)
	at kg.o(SourceFile:654)
	at uw.o_(SourceFile:175)
	at kg.h(SourceFile:192)
	at kl.a(SourceFile:195)
	at fd.a(SourceFile:136)
	at cv.b(SourceFile:64)
	at kl.e(SourceFile:63)
	at ko.b(SourceFile:37)
	at bnq.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	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 ou.a(SourceFile:523)
	at kg.a(SourceFile:677)
	at ou.c(SourceFile:493)
	at zj.b(SourceFile:79)
	at yx.b(SourceFile:116)
	at uw.o(SourceFile:294)
	at kg.o(SourceFile:654)
	at uw.o_(SourceFile:175)

-- Player being ticked --
Details:
	Entity Type: null (kg)
	Entity ID: 82039
	Entity Name: albin900
	Entity's Exact location: 502,39, 69,00, -557,19
	Entity's Block location: World: (502,69,-558), Chunk: (at 6,4,2 in 31,-35; contains blocks 496,0,-560 to 511,255,-545), Region: (0,-2; contains chunks 0,-64 to 31,-33, blocks 0,0,-1024 to 511,255,-513)
	Entity's Momentum: 0,00, -0,08, 0,00
Stacktrace:
	at kg.h(SourceFile:192)
	at kl.a(SourceFile:195)
	at fd.a(SourceFile:136)
	at cv.b(SourceFile:64)
	at kl.e(SourceFile:63)

-- Ticking connection --
Details:
	Connection: kl@5a74d6f
Stacktrace:
	at ko.b(SourceFile:37)
	at bnq.b(SourceFile:84)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	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_15, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 165892824 bytes (158 MB) / 508690432 bytes (485 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 4514 (252784 bytes; 0 MB) allocated, 4364 (244384 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 2028 (113568 bytes; 0 MB) allocated, 1814 (101584 bytes; 0 MB) used
	Player Count: 1 / 8; [kg['albin900'/82039, l='13w36a', x=502,39, y=69,00, z=-557,19]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.