Custom Spawners of 1.5.2 Crash in 13w22a

I made two custom mob spawners in 1.5.2, using enchanted equipment, varied spawn rates and custom potion effects. I opened the world in 13w22a, it rendered and crashed in just a few seconds.

Crash Report:

---- Minecraft Crash Report ----
// Shall we play a game?

Time: 6/5/13 9:53 AM
Description: Loading entity NBT

java.lang.NullPointerException
	at np.a(SourceFile:357)
	at nq.a(SourceFile:251)
	at td.a(SourceFile:288)
	at sv.a(SourceFile:83)
	at mx.f(SourceFile:1061)
	at aas.a(SourceFile:116)
	at aas.h(SourceFile:234)
	at bhk.a(SourceFile:22)
	at bhk.a(SourceFile:17)
	at bhk.a(SourceFile:12)
	at bhp.a(SourceFile:106)
	at bhp.a(SourceFile:98)
	at bdz.a(SourceFile:317)
	at bds.a(SourceFile:836)
	at bds.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 np.a(SourceFile:357)
	at nq.a(SourceFile:251)
	at td.a(SourceFile:288)
	at sv.a(SourceFile:83)

-- Entity being loaded --
Details:
	Entity Type: PigZombie (sv)
	Entity ID: 322
	Entity Name: Zombie Pigman
	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 bhk.a(SourceFile:22)
	at bhk.a(SourceFile:17)
	at bhk.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: (-641,4,1827), Chunk: (at 15,0,3 in -41,114; contains blocks -656,0,1824 to -641,255,1839), Region: (-2,3; contains chunks -64,96 to -33,127, blocks -1024,0,1536 to -513,255,2047)
	Actual block type: ID #52 (tile.mobSpawner // aol)
	Actual block data value: 0 / 0x0 / 0b0000
Stacktrace:
	at bhp.a(SourceFile:106)
	at bhp.a(SourceFile:98)
	at bdz.a(SourceFile:317)
	at bds.a(SourceFile:836)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bbw['Avantir_Yihn'/94, l='MpServer', x=-632.83, y=8.15, z=1827.85]]
	Chunk stats: MultiplayerChunkCache: 55
	Level seed: 0
	Level generator: ID 01 - flat, ver 0. Features enabled: false
	Level generator options: 
	Level spawn location: World: (-648,32,1738), Chunk: (at 8,2,10 in -41,108; contains blocks -656,0,1728 to -641,255,1743), Region: (-2,3; contains chunks -64,96 to -33,127, blocks -1024,0,1536 to -513,255,2047)
	Level time: 1662092 game time, 3829 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: 13 total; [rg['Pig'/68, l='MpServer', x=-592.22, y=4.00, z=1872.50], rz['Falling Block'/64, l='MpServer', x=-616.50, y=6.19, z=1791.50], rz['Falling Block'/65, l='MpServer', x=-617.50, y=6.19, z=1791.50], rz['Falling Block'/66, l='MpServer', x=-618.50, y=6.19, z=1791.50], rz['Falling Block'/67, l='MpServer', x=-618.50, y=5.29, z=1792.50], rg['Pig'/43, l='MpServer', x=-680.03, y=4.00, z=1794.91], rg['Pig'/81, l='MpServer', x=-581.03, y=8.16, z=1859.03], sg['entity.MinecartRideable.name'/80, l='MpServer', x=-577.22, y=4.69, z=1788.22], rg['Pig'/83, l='MpServer', x=-564.59, y=4.00, z=1806.13], rg['Pig'/82, l='MpServer', x=-571.81, y=4.00, z=1790.25], rz['Falling Block'/63, l='MpServer', x=-618.50, y=6.19, z=1790.50], rz['Falling Block'/62, l='MpServer', x=-617.50, y=6.19, z=1790.50], bbw['Avantir_Yihn'/94, l='MpServer', x=-632.83, y=8.15, z=1827.85]]
	Retry entities: 0 total; []
Stacktrace:
	at bbt.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: 13w22a
	Operating System: Mac OS X (x86_64) version 10.7.5
	Java Version: 1.6.0_45, Apple Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Apple Inc.
	Memory: 46457184 bytes (44 MB) / 124915712 bytes (119 MB) up to 1069416448 bytes (1019 MB)
	JVM Flags: 1 total; -Xmx1G
	AABB Pool Size: 9251 (518056 bytes; 0 MB) allocated, 2411 (135016 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
	LWJGL: 2.9.0
	OpenGL: ATI Radeon HD 2600 PRO OpenGL Engine GL version 2.1 ATI-7.32.12, ATI Technologies Inc.
	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: 511 (28616 bytes; 0 MB) allocated, 511 (28616 bytes; 0 MB) used