[MC-16290] [crash] mob spawner crashing game

It seems like mob spawners are crashing the game, cause the new attributes on the mobs.
I created a standard mob spawner in mc edit. All works fine, but if i enter the world in minecraft, it crashes instantly.
If i move the spawner away in an unloaded chunk minecraft works fine, until it´s trying to load the spawner. So it has to be the spawner i guess.
Crash report:
---- Minecraft Crash Report ----
// Hi. I'm Minecraft, and I'm a crashaholic.

Time: 24.05.13 00:41
Description: Loading entity NBT

java.lang.UnsupportedOperationException: Cannot modify readonly attribute
	at oi.a(SourceFile:54)
	at sx.a(SourceFile:87)
	at sx.a(SourceFile:70)
	at np.a(SourceFile:348)
	at nq.a(SourceFile:251)
	at sn.a(SourceFile:84)
	at mx.f(SourceFile:1061)
	at aas.a(SourceFile:116)
	at aas.h(SourceFile:234)
	at bhe.a(SourceFile:22)
	at bhe.a(SourceFile:17)
	at bhe.a(SourceFile:12)
	at bhj.a(SourceFile:106)
	at bhj.a(SourceFile:98)
	at bdt.a(SourceFile:317)
	at bdm.a(SourceFile:836)
	at bdm.b(SourceFile:682)
	at asx.R(SourceFile:674)
	at asx.d(SourceFile:607)
	at net.minecraft.client.main.Main.main(SourceFile:78)


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

-- Head --
Stacktrace:
	at oi.a(SourceFile:54)
	at sx.a(SourceFile:87)
	at sx.a(SourceFile:70)
	at np.a(SourceFile:348)
	at nq.a(SourceFile:251)
	at sn.a(SourceFile:84)

-- Entity being loaded --
Details:
	Entity Type: Creeper (sn)
	Entity ID: 4535
	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 mx.f(SourceFile:1061)
	at aas.a(SourceFile:116)
	at aas.h(SourceFile:234)
	at bhe.a(SourceFile:22)
	at bhe.a(SourceFile:17)
	at bhe.a(SourceFile:12)

-- Tile Entity Details --
Details:
	Name: MobSpawner // arm
	Block type: ID #52 (tile.mobSpawner // aol)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (-310,56,-362), Chunk: (at 10,3,6 in -20,-23; contains blocks -320,0,-368 to -305,255,-353), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Actual block type: ID #52 (tile.mobSpawner // aol)
	Actual block data value: 0 / 0x0 / 0b0000
Stacktrace:
	at bhj.a(SourceFile:106)
	at bhj.a(SourceFile:98)
	at bdt.a(SourceFile:317)
	at bdm.a(SourceFile:836)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bbq['RF_Darter'/4390, l='MpServer', x=-309,90, y=57,62, z=-359,97]]
	Chunk stats: MultiplayerChunkCache: 30
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-279,4,-348), Chunk: (at 9,0,4 in -18,-22; contains blocks -288,0,-352 to -273,255,-337), Region: (-1,-1; contains chunks -32,-32 to -1,-1, blocks -512,0,-512 to -1,255,-1)
	Level time: 11941 game time, 11941 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: 3 total; [bbq['RF_Darter'/4390, l='MpServer', x=-309,90, y=57,62, z=-359,97], sn['Creeper'/4389, l='MpServer', x=-286,75, y=56,00, z=-361,50], rf['Ocelot'/4388, l='MpServer', x=-328,22, y=56,00, z=-333,84]]
	Retry entities: 0 total; []
Stacktrace:
	at bbn.a(SourceFile:282)
	at asx.b(SourceFile:1793)
	at asx.d(SourceFile:616)
	at net.minecraft.client.main.Main.main(SourceFile:78)

-- System Details --
Details:
	Minecraft Version: 13w21a
	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: 195029752 bytes (185 MB) / 384565248 bytes (366 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 21638 (1211728 bytes; 1 MB) allocated, 94 (5264 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	LWJGL: 2.9.0
	OpenGL: GeForce GT 540M/PCIe/SSE2 GL version 4.2.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: Default
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 156 (8736 bytes; 0 MB) allocated, 59 (3304 bytes; 0 MB) used