Hopper: java.lang.NullPointerException

This is an automatically generated report based from the following crash: http://hopper.minecraft.net/crashes/minecraft/MCX-73289/

Crash:

java.lang.NullPointerException
	at adv.a(SourceFile:82)
	at adt.<init>(SourceFile:26)
	at ads.a(SourceFile:52)
	at ads.d(SourceFile:87)
	at adv.a(SourceFile:160)
	at adv.b(SourceFile:150)
	at agb.d(SourceFile:194)
	at kc.c(SourceFile:72)
	at kb.<init>(SourceFile:28)
	at ka.a(SourceFile:209)
	at ka.a(SourceFile:246)
	at hx.a(SourceFile:151)
	at hx.c(SourceFile:199)
	at hx.a(SourceFile:95)
	at bnj.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	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 ----
// You're mean.

Time: 9/5/13 11:21 AM
Description: Invalid Biome id

java.lang.NullPointerException
	at adv.a(SourceFile:82)
	at adt.<init>(SourceFile:26)
	at ads.a(SourceFile:52)
	at ads.d(SourceFile:87)
	at adv.a(SourceFile:160)
	at adv.b(SourceFile:150)
	at agb.d(SourceFile:194)
	at kc.c(SourceFile:72)
	at kb.<init>(SourceFile:28)
	at ka.a(SourceFile:209)
	at ka.a(SourceFile:246)
	at hx.a(SourceFile:151)
	at hx.c(SourceFile:199)
	at hx.a(SourceFile:95)
	at bnj.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	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: -96
	z: -1168
	w: 16
	h: 16
Stacktrace:
	at adv.a(SourceFile:82)
	at adt.<init>(SourceFile:26)
	at ads.a(SourceFile:52)
	at ads.d(SourceFile:87)
	at adv.a(SourceFile:160)
	at adv.b(SourceFile:150)
	at agb.d(SourceFile:194)

-- Chunk to be generated --
Details:
	Location: -6,-73
	Position hash: -309237645318
	Generator: RandomLevelSource
Stacktrace:
	at kc.c(SourceFile:72)
	at kb.<init>(SourceFile:28)
	at ka.a(SourceFile:209)
	at ka.a(SourceFile:246)
	at hx.a(SourceFile:151)
	at hx.c(SourceFile:199)
	at hx.a(SourceFile:95)
	at bnj.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:481)
	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 XP (x86) version 5.1
	Java Version: 1.7.0_25, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 298768392 bytes (284 MB) / 517812224 bytes (493 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 1040 (58240 bytes; 0 MB) allocated, 1040 (58240 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: 0, tcache: 0, allocated: 14, tallocated: 122
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 450 (25200 bytes; 0 MB) allocated, 450 (25200 bytes; 0 MB) used
	Player Count: 1 / 8; [kg['joemassdsd'/145572, l='1.7 snapshot', x=66.64, y=90.61, z=-1100.73]]
	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-73289/8104604/