Crash when spawning invisible mob

When I create a spawner that spawns an invisible mob the game crashes.
Here is the crash report:

---- Minecraft Crash Report ----

Time: 6/7/13 5:23 PM
Description: Loading entity NBT

java.lang.NullPointerException
	at nr.a(SourceFile:357)
	at ns.a(SourceFile:251)
	at sr.a(SourceFile:84)
	at mz.f(SourceFile:1061)
	at aaw.a(SourceFile:116)
	at aaw.h(SourceFile:234)
	at bhs.a(SourceFile:22)
	at bhs.a(SourceFile:17)
	at bhs.a(SourceFile:12)
	at bhx.a(SourceFile:106)
	at bhx.a(SourceFile:98)
	at beh.a(SourceFile:317)
	at bea.a(SourceFile:834)
	at bea.b(SourceFile:682)
	at atb.R(SourceFile:683)
	at atb.d(SourceFile:616)
	at net.minecraft.client.main.Main.main(SourceFile:79)


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

-- Head --
Stacktrace:
	at nr.a(SourceFile:357)
	at ns.a(SourceFile:251)
	at sr.a(SourceFile:84)

-- Entity being loaded --
Details:
	Entity Type: Creeper (sr)
	Entity ID: 5374
	Entity Name: Creeper
	Entity's Exact location: 0.00, 0.00, 0.00
	Entity's Block location: World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Entity's Momentum: 0.00, -0.08, 0.00
Stacktrace:
	at mz.f(SourceFile:1061)
	at aaw.a(SourceFile:116)
	at aaw.h(SourceFile:234)
	at bhs.a(SourceFile:22)
	at bhs.a(SourceFile:17)
	at bhs.a(SourceFile:12)

-- Tile Entity Details --
Details:
	Name: MobSpawner // arq
	Block type: ID #52 (tile.mobSpawner // aop)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (51,25,-261), Chunk: (at 3,1,11 in 3,-17; contains blocks 48,0,-272 to 63,255,-257), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Actual block type: ID #52 (tile.mobSpawner // aop)
	Actual block data value: 0 / 0x0 / 0b0000
Stacktrace:
	at bhx.a(SourceFile:106)
	at bhx.a(SourceFile:98)
	at beh.a(SourceFile:317)
	at bea.a(SourceFile:834)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bce['nitroee'/703, l='MpServer', x=67.86, y=29.49, z=-260.25]]
	Chunk stats: MultiplayerChunkCache: 40
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (101,25,-301), Chunk: (at 5,1,3 in 6,-19; contains blocks 96,0,-304 to 111,255,-289), Region: (0,-1; contains chunks 0,-32 to 31,-1, blocks 0,0,-512 to 511,255,-1)
	Level time: 6354503 game time, 9147 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: 12 total; [te['Slime'/186, l='MpServer', x=121.25, y=25.00, z=-226.06], te['Slime'/102, l='MpServer', x=33.09, y=25.00, z=-274.66], nq['entity.LeashKnot.name'/702, l='MpServer', x=91.50, y=25.50, z=-295.50], rc['Chicken'/187, l='MpServer', x=126.91, y=25.00, z=-222.78], rl['Sheep'/154, l='MpServer', x=90.16, y=25.00, z=-295.19], re['Mule'/155, l='MpServer', x=93.41, y=25.00, z=-295.34], nq['entity.LeashKnot.name'/701, l='MpServer', x=91.50, y=25.50, z=-294.50], se['item.item.egg'/156, l='MpServer', x=88.72, y=25.13, z=-289.88], rc['Chicken'/106, l='MpServer', x=57.56, y=25.00, z=-209.56], rc['Chicken'/122, l='MpServer', x=79.63, y=25.00, z=-283.63], sk['entity.MinecartRideable.name'/105, l='MpServer', x=53.72, y=24.69, z=-278.34], bce['nitroee'/703, l='MpServer', x=67.86, y=29.49, z=-260.25]]
	Retry entities: 0 total; []
Stacktrace:
	at bcb.a(SourceFile:282)
	at atb.b(SourceFile:1795)
	at atb.d(SourceFile:625)
	at net.minecraft.client.main.Main.main(SourceFile:79)

-- System Details --
Details:
	Minecraft Version: 13w23a
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_07, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 200885632 bytes (191 MB) / 357367808 bytes (340 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 21635 (1211560 bytes; 1 MB) allocated, 1833 (102648 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	Launched Version: 13w23a
	LWJGL: 2.9.0
	OpenGL: GeForce 8600 GT/PCIe/SSE2 GL version 3.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: Tweaked Default.zip
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 303 (16968 bytes; 0 MB) allocated, 303 (16968 bytes; 0 MB) used