Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-72133/

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.a(SourceFile:1032)
	at bhh.i(SourceFile:1191)
	at bhh.a(SourceFile:787)
	at bhh.b(SourceFile:695)
	at avx.V(SourceFile:713)
	at avx.e(SourceFile:642)
	at net.minecraft.client.main.Main.main(SourceFile:103)

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

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 5/09/13 16:02
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.a(SourceFile:1032)
	at bhh.i(SourceFile:1191)
	at bhh.a(SourceFile:787)
	at bhh.b(SourceFile:695)
	at avx.V(SourceFile:713)
	at avx.e(SourceFile:642)
	at net.minecraft.client.main.Main.main(SourceFile:103)


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

-- DownfallBlock --
Details:
	downfalls[] size: 256
	x: 0
	z: 0
	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.a(SourceFile:1032)
	at bhh.i(SourceFile:1191)
	at bhh.a(SourceFile:787)

-- Affected level --
Details:
	Level name: MpServer
	All players: 1 total; [bfg['Ian_Cholo'/238, l='MpServer', x=8,50, y=66,62, z=8,50]]
	Chunk stats: MultiplayerChunkCache: 0, 0
	Level seed: 0
	Level generator: ID 00 - default, ver 1. Features enabled: false
	Level generator options: 
	Level spawn location: World: (208,64,248), Chunk: (at 0,4,8 in 13,15; contains blocks 208,0,240 to 223,255,255), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
	Level time: 13057 game time, 13625 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; [bfg['Ian_Cholo'/238, l='MpServer', x=8,50, y=66,62, z=8,50]]
	Retry entities: 0 total; []
	Server brand: vanilla
	Server type: Integrated singleplayer server
Stacktrace:
	at bfb.a(SourceFile:285)
	at avx.b(SourceFile:1813)
	at avx.e(SourceFile:651)
	at net.minecraft.client.main.Main.main(SourceFile:103)

-- System Details --
Details:
	Minecraft Version: 13w36a
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.7.0_17, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 104463784 bytes (99 MB) / 197918720 bytes (188 MB) up to 954466304 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	AABB Pool Size: 10819 (605864 bytes; 0 MB) allocated, 10819 (605864 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: 1, tcache: 1, allocated: 12, tallocated: 94
	Launched Version: 13w36a
	LWJGL: 2.9.0
	OpenGL: GeForce GT 520M/PCIe/SSE2 GL version 4.3.0, NVIDIA Corporation
	Is Modded: Probably not. Jar signature remains and client brand is untouched.
	Type: Client (map_client.txt)
	Resource Packs: []
	Current Language: Español (España)
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 12 (672 bytes; 0 MB) allocated, 12 (672 bytes; 0 MB) used

You can see this full report at http://hopper.minecraft.net/crashes/minecraft/MCX-72133/8088276/