Hopper: java.lang.NullPointerException

java.lang.NullPointerException
	at ou.b(SourceFile:536)
	at ou.aL(SourceFile:399)
	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 oc.W(SourceFile:1164)
	at ou.W(SourceFile:1368)
	at act.a(SourceFile:1363)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)
	at act.a(SourceFile:1402)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)

---- Minecraft Crash Report ----
// This doesn't make any sense!

Time: 9/6/13 5:44 PM
Description: Ticking entity

java.lang.NullPointerException
	at ou.b(SourceFile:536)
	at ou.aL(SourceFile:399)
	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 oc.W(SourceFile:1164)
	at ou.W(SourceFile:1368)
	at act.a(SourceFile:1363)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)
	at act.a(SourceFile:1402)
	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 ou.b(SourceFile:536)
	at ou.aL(SourceFile:399)
	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 oc.W(SourceFile:1164)
	at ou.W(SourceFile:1368)
	at act.a(SourceFile:1363)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)
	at act.a(SourceFile:1402)
	at kd.a(SourceFile:479)
	at act.g(SourceFile:1343)

-- Entity being ticked --
Details:
	Entity Type: MinecartRideable (tp)
	Entity ID: 95671
	Entity Name: entity.MinecartRideable.name
	Entity's Exact location: 823.50, 69.31, 1321.50
	Entity's Block location: World: (823,69,1321), Chunk: (at 7,4,9 in 51,82; contains blocks 816,0,1312 to 831,255,1327), Region: (1,2; contains chunks 32,64 to 63,95, blocks 512,0,1024 to 1023,255,1535)
	Entity's Momentum: 0.00, -0.04, 0.00
Stacktrace:
	at act.h(SourceFile:1250)
	at kd.h(SourceFile:364)

-- Affected level --
Details:
	Level name: 13w36a
	All players: 1 total; [kg['pcgrosen'/290, l='13w36a', x=817.34, y=64.00, z=1322.51]]
	Chunk stats: ServerChunkCache: 885 Drop: 0
	Level seed: -5788666010862474413
	Level generator: ID 03 - amplified, ver 0. Features enabled: true
	Level generator options: 
	Level spawn location: World: (224,64,256), Chunk: (at 0,4,0 in 14,16; contains blocks 224,0,256 to 239,255,271), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 122693 game time, 8786 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 54937 (now: false), thunder time: 131075 (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 8 (amd64) version 6.2
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 65025216 bytes (62 MB) / 413270016 bytes (394 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 1349 (75544 bytes; 0 MB) allocated, 1224 (68544 bytes; 0 MB) used
	IntCache: cache: 0, tcache: 0, allocated: 12, tallocated: 94
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 220 (12320 bytes; 0 MB) allocated, 207 (11592 bytes; 0 MB) used
	Player Count: 1 / 8; [kg['pcgrosen'/290, l='13w36a', x=817.34, y=64.00, z=1322.51]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.