Monster Spawner Crash

I create a monster spawner with MCEdit and when i load the map, Minecraft crash

Crash Report :

---- Minecraft Crash Report ----
// Oh - I know what I did wrong!

Time: 25/05/13 10:50
Description: Rendering Tile Entity

java.lang.NullPointerException
	at aas.a(SourceFile:110)
	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:684)
	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 aas.a(SourceFile:110)
	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: (987,57,-233), Chunk: (at 11,3,7 in 61,-15; contains blocks 976,0,-240 to 991,255,-225), Region: (1,-1; contains chunks 32,-32 to 63,-1, blocks 512,0,-512 to 1023,255,-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['solal2003'/22691, l='MpServer', x=987,75, y=60,03, z=-235,30]]
	Chunk stats: MultiplayerChunkCache: 50
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (1038,4,-256), Chunk: (at 14,0,0 in 64,-16; contains blocks 1024,0,-256 to 1039,255,-241), Region: (2,-1; contains chunks 64,-32 to 95,-1, blocks 1024,0,-512 to 1535,255,-1)
	Level time: 363531 game time, 131322 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: 1 total; [bbq['solal2003'/22691, l='MpServer', x=987,75, y=60,03, z=-235,30]]
	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: Mac OS X (x86_64) version 10.8.3
	Java Version: 1.6.0_45, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 102659544 bytes (97 MB) / 237674496 bytes (226 MB) up to 1065025536 bytes (1015 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 21638 (1211728 bytes; 1 MB) allocated, 2 (112 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	LWJGL: 2.9.0
	OpenGL: Intel HD Graphics 3000 OpenGL Engine GL version 2.1 INTEL-8.10.44, Intel Inc.
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Texture Pack: John-Smith-1.5
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 191 (10696 bytes; 0 MB) allocated, 46 (2576 bytes; 0 MB) used