I Crashed!

I put around 30,000 creepers through an end portal. I jumped in. I was getting about 0.1 fps. After a couple minutes, I heard a explosion. I got the out of memory screen. Then, I crashed:

--- BEGIN ERROR REPORT 9d472e94 --------
Full report at:
C:\Users\John\AppData\Roaming\.minecraft\crash-reports\crash-2013-03-09_22.55.43-server.txt
Please show that file to Mojang, NOT just this screen!

Generated 3/9/13 10:55 PM

-- Head --
Stacktrace:
	at aqt.a(SourceFile:23)
	at aou.b(SourceFile:567)
	at aou.a(SourceFile:562)
	at zv.a(SourceFile:935)
	at mp.d(SourceFile:481)
	at ng.e(SourceFile:977)
	at ng.c(SourceFile:1185)
	at rv.c(SourceFile:26)
	at ng.l_(SourceFile:551)
	at rv.l_(SourceFile:31)
	at ro.l_(SourceFile:108)
	at zv.a(SourceFile:1336)
	at iz.a(SourceFile:508)
	at zv.g(SourceFile:1314)

-- Entity being ticked --
Details:
	Entity Type: Creeper (ro)
	Entity ID: 2528962
	Entity Name: Creeper
	Entity's Exact location: 99.64, 50.36, 0.33
	Entity's Block location: World: (99,50,0), Chunk: (at 3,3,0 in 6,0; contains blocks 96,0,0 to 111,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Entity's Momentum: -227.52, 1.26, 210.87
Stacktrace:
	at zv.h(SourceFile:1221)
	at iz.h(SourceFile:390)

-- Affected level --
Details:
	Level name: Test World (Non Mob Spawners)
	All players: 1 total; [jc['DeEpicness123'/730264, l='Test World (Non Mob Spawners)', x=100.00, y=49.00, z=0.00]]
	Chunk stats: ServerChunkCache: 442 Drop: 0
	Level seed: 516595084
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn 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)
	Level time: 0 game time, 0 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: ~~ERROR~~ NullPointerException: null
Stacktrace:
	at net.minecraft.server.MinecraftServer.r(SourceFile:462)
	at net.minecraft.server.MinecraftServer.q(SourceFile:397)
	at bja.q(SourceFile:122)
	at net.minecraft.server.MinecraftServer.run(SourceFile:331)
	at gp.run(SourceFile:573)

-- System Details --
Details:
	Minecraft Version: 1.5
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.6.0_31, Sun Microsystems Inc.
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Sun Microsystems Inc.
	Memory: 56849664 bytes (54 MB) / 1041694720 bytes (993 MB) up to 1041694720 bytes (993 MB)
	JVM Flags: 2 total; -Xms512m -Xmx1024m
	AABB Pool Size: 8835157 (494768792 bytes; 471 MB) allocated, 8835157 (494768792 bytes; 471 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 0, tcache: 0, allocated: 1, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 33 (1848 bytes; 0 MB) allocated, 17 (952 bytes; 0 MB) used
	Player Count: 1 / 8; [jc['DeEpicness123'/730264, l='Test World (Non Mob Spawners)', x=100.00, y=49.00, z=0.00]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

java.lang.OutOfMemoryError: Java heap space
	at aqt.a(SourceFile:23)
	at aou.b(SourceFile:567)
	at aou.a(SourceFile:562)
	at zv.a(SourceFile:935)
	at mp.d(SourceFile:481)
	at ng.e(SourceFile:977)
	at ng.c(SourceFile:1185)
	at rv.c(SourceFile:26)
	at ng.l_(SourceFile:551)
	at rv.l_(SourceFile:31)
	at ro.l_(SourceFile:108)
	at zv.a(SourceFile:1336)
	at iz.a(SourceFile:508)
	at zv.g(SourceFile:1314)
	at zv.h(SourceFile:1221)
	at iz.h(SourceFile:390)
	at net.minecraft.server.MinecraftServer.r(SourceFile:462)
	at net.minecraft.server.MinecraftServer.q(SourceFile:397)
	at bja.q(SourceFile:122)
	at net.minecraft.server.MinecraftServer.run(SourceFile:331)
	at gp.run(SourceFile:573)
--- END ERROR REPORT 31ba3297 ----------