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 act.a(SourceFile:1365)
	at act.g(SourceFile:1343)

---- Minecraft Crash Report ----
// Quite honestly, I wouldn't worry myself about that.

Time: 9/6/13 11:31 PM
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 act.a(SourceFile:1365)
	at act.g(SourceFile:1343)
	at act.h(SourceFile:1250)
	at awb.m(SourceFile:1426)
	at awb.V(SourceFile:686)
	at awb.e(SourceFile:642)
	at net.minecraft.client.main.Main.main(SourceFile:103)


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 act.a(SourceFile:1365)
	at act.g(SourceFile:1343)

-- Entity being ticked --
Details:
	Entity Type: Cow (sg)
	Entity ID: 36292
	Entity Name: Cow
	Entity's Exact location: 1001.50, 57.00, 967.50
	Entity's Block location: World: (1001,57,967), Chunk: (at 9,3,7 in 62,60; contains blocks 992,0,960 to 1007,255,975), Region: (1,1; contains chunks 32,32 to 63,63, blocks 512,0,512 to 1023,255,1023)
	Entity's Momentum: 0.00, 0.00, 0.00
Stacktrace:
	at act.h(SourceFile:1250)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bfn['123panda321'/112, l='MpServer', x=1003.46, y=57.62, z=966.71]]
	Chunk stats: MultiplayerChunkCache: 225, 225
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (1002,4,965), Chunk: (at 10,0,5 in 62,60; contains blocks 992,0,960 to 1007,255,975), Region: (1,1; contains chunks 32,32 to 63,63, blocks 512,0,512 to 1023,255,1023)
	Level time: 18293 game time, 18293 day time
	Level dimension: 0
	Level storage version: 0x00000 - Unknown?
	Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
	Level game mode: Game mode: creative (ID 1). Hardcore: false. Cheats: false
	Forced entities: 68 total; [uk['Spider'/32899, l='MpServer', x=1077.97, y=56.00, z=941.03], tw['Creeper'/21265, l='MpServer', x=1029.50, y=56.00, z=887.50], sg['Cow'/36292, l='MpServer', x=1001.50, y=57.00, z=967.50], sg['Cow'/23, l='MpServer', x=948.53, y=56.00, z=972.22], tj['item.item.leather'/12412, l='MpServer', x=984.59, y=56.13, z=918.25], tj['item.item.beefRaw'/12414, l='MpServer', x=984.66, y=56.13, z=918.75], tw['Creeper'/26406, l='MpServer', x=1082.50, y=56.00, z=927.50], tw['Creeper'/28304, l='MpServer', x=994.50, y=56.00, z=1024.50], sg['Cow'/32, l='MpServer', x=1014.01, y=59.30, z=978.89], sd['Bat'/33, l='MpServer', x=1014.01, y=58.62, z=978.89], uk['Spider'/7377, l='MpServer', x=1062.47, y=56.00, z=1005.06], sg['Cow'/39, l='MpServer', x=974.69, y=56.00, z=948.28], sg['Cow'/42, l='MpServer', x=974.25, y=56.00, z=985.38], sg['Cow'/43, l='MpServer', x=980.75, y=56.00, z=1005.22], ui['Skeleton'/28312, l='MpServer', x=993.50, y=56.00, z=1019.50], sg['Cow'/40, l='MpServer', x=977.31, y=56.00, z=985.72], bfn['123panda321'/112, l='MpServer', x=1003.46, y=57.62, z=966.71], sg['Cow'/41, l='MpServer', x=964.09, y=56.00, z=973.66], un['Zombie'/26389, l='MpServer', x=1049.50, y=56.00, z=987.50], uk['Spider'/35005, l='MpServer', x=1025.13, y=56.00, z=936.47], un['Zombie'/26390, l='MpServer', x=1047.50, y=56.00, z=990.50], sg['Cow'/51, l='MpServer', x=1003.69, y=56.00, z=962.59], sg['Cow'/50, l='MpServer', x=981.13, y=56.00, z=937.97], sg['Cow'/55, l='MpServer', x=1006.34, y=56.00, z=929.25], sg['Cow'/54, l='MpServer', x=999.88, y=56.00, z=964.06], sg['Cow'/53, l='MpServer', x=1012.16, y=56.00, z=939.91], sg['Cow'/59, l='MpServer', x=1007.06, y=56.00, z=961.09], sg['Cow'/58, l='MpServer', x=1033.69, y=56.00, z=954.28], sg['Cow'/57, l='MpServer', x=999.28, y=56.00, z=973.28], sg['Cow'/56, l='MpServer', x=989.81, y=56.00, z=944.19], sg['Cow'/62, l='MpServer', x=1011.78, y=56.00, z=953.94], sg['Cow'/61, l='MpServer', x=986.22, y=56.00, z=984.88], sg['Cow'/60, l='MpServer', x=995.22, y=56.00, z=974.25], tw['Creeper'/33119, l='MpServer', x=950.50, y=56.00, z=941.50], uk['Spider'/23502, l='MpServer', x=959.19, y=56.00, z=965.81], tw['Creeper'/33118, l='MpServer', x=958.16, y=56.00, z=953.22], sg['Cow'/69, l='MpServer', x=988.25, y=56.00, z=936.69], tw['Creeper'/33117, l='MpServer', x=954.50, y=56.00, z=945.50], sg['Cow'/70, l='MpServer', x=1006.03, y=56.00, z=953.88], un['Zombie'/23501, l='MpServer', x=968.88, y=56.00, z=958.75], sg['Cow'/71, l='MpServer', x=1002.28, y=56.00, z=941.22], un['Zombie'/23498, l='MpServer', x=964.88, y=56.00, z=958.59], sg['Cow'/65, l='MpServer', x=1020.91, y=56.00, z=925.03], sg['Cow'/78, l='MpServer', x=1052.94, y=56.00, z=894.09], sg['Cow'/72, l='MpServer', x=1032.19, y=56.00, z=950.22], uk['Spider'/15473, l='MpServer', x=1057.59, y=56.00, z=997.97], sg['Cow'/73, l='MpServer', x=1013.72, y=56.00, z=999.34], sg['Cow'/75, l='MpServer', x=1061.63, y=56.00, z=921.84], uk['Spider'/35015, l='MpServer', x=1029.78, y=56.00, z=924.41], tw['Creeper'/35009, l='MpServer', x=1027.50, y=56.00, z=925.50], tw['Creeper'/35011, l='MpServer', x=1028.50, y=56.00, z=925.50], ui['Skeleton'/26365, l='MpServer', x=962.50, y=56.00, z=1001.50], ui['Skeleton'/26363, l='MpServer', x=968.25, y=56.00, z=1003.31], uk['Spider'/23504, l='MpServer', x=967.34, y=56.00, z=975.28], sg['Cow'/2170, l='MpServer', x=989.88, y=56.00, z=960.94], ui['Skeleton'/32895, l='MpServer', x=1083.50, y=56.00, z=934.50], ui['Skeleton'/29787, l='MpServer', x=1021.50, y=56.00, z=1019.50], ui['Skeleton'/25480, l='MpServer', x=1059.50, y=56.00, z=962.84], sg['Cow'/3384, l='MpServer', x=1013.06, y=56.00, z=980.03], ui['Skeleton'/29785, l='MpServer', x=1024.50, y=56.00, z=1019.50], tj['item.item.leather'/10180, l='MpServer', x=958.09, y=56.13, z=1001.84], tj['item.item.beefRaw'/10182, l='MpServer', x=957.91, y=56.13, z=1002.66], tw['Creeper'/33120, l='MpServer', x=949.50, y=56.00, z=941.50], uk['Spider'/29782, l='MpServer', x=1020.50, y=56.00, z=1028.50], uk['Spider'/29780, l='MpServer', x=1021.50, y=56.00, z=1025.50], ui['Skeleton'/25479, l='MpServer', x=1058.50, y=56.00, z=968.50], tw['Creeper'/25478, l='MpServer', x=1014.16, y=56.00, z=987.91], ui['Skeleton'/18079, l='MpServer', x=1026.50, y=56.00, z=896.50]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bfi.a(SourceFile:285)
	at awb.b(SourceFile:1813)
	at awb.e(SourceFile:651)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w36b
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_09, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 133270688 bytes (127 MB) / 390594560 bytes (372 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 1088 (60928 bytes; 0 MB) allocated, 1079 (60424 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 13w36b
	LWJGL: 2.9.0
	OpenGL: GeForce 6800/PCIe/SSE2 GL version 2.1.2, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: English (UK)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 189 (10584 bytes; 0 MB) allocated, 154 (8624 bytes; 0 MB) used