Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-74154/

Crash:

java.lang.NullPointerException
	at adv.a(SourceFile:82)
	at adt.<init>(SourceFile:26)
	at ads.a(SourceFile:52)
	at ads.b(SourceFile:61)
	at adv.a(SourceFile:61)
	at aey.a(SourceFile:926)
	at act.a(SourceFile:100)
	at act.d(SourceFile:1926)
	at act.y(SourceFile:1922)
	at kd.g(SourceFile:258)
	at kd.b(SourceFile:134)
	at net.minecraft.server.MinecraftServer.t(SourceFile:455)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bng.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hs.run(SourceFile:575)

The following is the first clean report made public about this crash:

---- Minecraft Crash Report ----
// This is a token for 1 free hug. Redeem at your nearest Mojangsta: [~~HUG~~]

Time: 05/09/13 17:22
Description: Invalid Biome id

java.lang.NullPointerException
	at adv.a(SourceFile:82)
	at adt.<init>(SourceFile:26)
	at ads.a(SourceFile:52)
	at ads.b(SourceFile:61)
	at adv.a(SourceFile:61)
	at aey.a(SourceFile:926)
	at act.a(SourceFile:100)
	at act.d(SourceFile:1926)
	at act.y(SourceFile:1922)
	at kd.g(SourceFile:258)
	at kd.b(SourceFile:134)
	at net.minecraft.server.MinecraftServer.t(SourceFile:455)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bng.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hs.run(SourceFile:575)


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

-- DownfallBlock --
Details:
	downfalls[] size: 256
	x: 16
	z: 96
	w: 16
	h: 16
Stacktrace:
	at adv.a(SourceFile:82)
	at adt.<init>(SourceFile:26)
	at ads.a(SourceFile:52)
	at ads.b(SourceFile:61)
	at adv.a(SourceFile:61)
	at aey.a(SourceFile:926)
	at act.a(SourceFile:100)
	at act.d(SourceFile:1926)
	at act.y(SourceFile:1922)
	at kd.g(SourceFile:258)
	at kd.b(SourceFile:134)

-- Affected level --
Details:
	Level name: Untitled World
	All players: 1 total; [kg['Captain_Jaffas'/195, l='Untitled World', x=-9.89, y=75.37, z=117.96]]
	Chunk stats: ServerChunkCache: 730 Drop: 0
	Level seed: -7388847942818539520
	Level generator: ID 00 - default, ver 1. Features enabled: true
	Level generator options: 
	Level spawn location: World: (0,65,0), Chunk: (at 0,4,0 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: 574 game time, 574 day time
	Level dimension: 0
	Level storage version: 0x04ABD - Anvil
	Level weather: Rain time: 84348 (now: false), thunder time: 103148 (now: false)
	Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
	at net.minecraft.server.MinecraftServer.t(SourceFile:455)
	at net.minecraft.server.MinecraftServer.s(SourceFile:398)
	at bng.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:332)
	at hs.run(SourceFile:575)

-- System Details --
Details:
	Minecraft Version: 13w36a
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 64318416 bytes (61 MB) / 186716160 bytes (178 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 3082 (172592 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Suspicious classes: [com.ibm.icu.text.ArabicShapingException], [gnu.trove.TIntCollection], [gnu.trove.impl.HashFunctions, PrimeFinder], [gnu.trove.impl.hash.THash, TPrimitiveHash, TIntIntHash], [gnu.trove.iterator.TIterator, TAdvancingIterator, TIntIntIterator], [gnu.trove.map.TIntIntMap], [gnu.trove.map.hash.TIntIntHashMap], [gnu.trove.procedure.TIntIntProcedure], [gnu.trove.set.TIntSet]
	IntCache: cache: 6, tcache: 55, allocated: 13, tallocated: 95
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 757 (42392 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
	Player Count: 1 / 8; [kg['Captain_Jaffas'/195, l='Untitled World', x=-9.89, y=75.37, z=117.96]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-74154/8119467/