Hopper: java.lang.ArrayIndexOutOfBoundsException: -1

java.lang.ArrayIndexOutOfBoundsException: -1
	at acv.b(SourceFile:114)
	at act.<init>(SourceFile:28)
	at acs.a(SourceFile:59)
	at acs.e(SourceFile:98)
	at acv.a(SourceFile:161)
	at acv.b(SourceFile:151)
	at aet.d(SourceFile:214)

---- Minecraft Crash Report ----
// You should try our sister game, Minceraft!

Time: 20/09/13 18:48
Description: Exception generating new chunk

java.lang.ArrayIndexOutOfBoundsException: -1
	at acv.b(SourceFile:114)
	at act.<init>(SourceFile:28)
	at acs.a(SourceFile:59)
	at acs.e(SourceFile:98)
	at acv.a(SourceFile:161)
	at acv.b(SourceFile:151)
	at aet.d(SourceFile:214)
	at jr.c(SourceFile:84)
	at jq.<init>(SourceFile:29)
	at jp.a(SourceFile:208)
	at jp.a(SourceFile:240)
	at hn.a(SourceFile:141)
	at hn.c(SourceFile:188)
	at hn.a(SourceFile:85)
	at blc.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)


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

-- Head --
Stacktrace:
	at acv.b(SourceFile:114)
	at act.<init>(SourceFile:28)
	at acs.a(SourceFile:59)
	at acs.e(SourceFile:98)
	at acv.a(SourceFile:161)
	at acv.b(SourceFile:151)
	at aet.d(SourceFile:214)

-- Chunk to be generated --
Details:
	Location: -7,-20
	Position hash: -81604378631
	Generator: RandomLevelSource
Stacktrace:
	at jr.c(SourceFile:84)
	at jq.<init>(SourceFile:29)
	at jp.a(SourceFile:208)
	at jp.a(SourceFile:240)
	at hn.a(SourceFile:141)
	at hn.c(SourceFile:188)
	at hn.a(SourceFile:85)
	at blc.b(SourceFile:73)
	at net.minecraft.server.MinecraftServer.t(SourceFile:489)
	at net.minecraft.server.MinecraftServer.s(SourceFile:406)
	at bkz.s(SourceFile:124)
	at net.minecraft.server.MinecraftServer.run(SourceFile:340)
	at hi.run(SourceFile:583)

-- System Details --
Details:
	Minecraft Version: 1.6.4
	Operating System: Windows 8 (x86) version 6.2
	Java Version: 1.7.0_40, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 98225856 bytes (93 MB) / 172273664 bytes (164 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	AABB Pool Size: 679 (38024 bytes; 0 MB) allocated, 643 (36008 bytes; 0 MB) used
	Suspicious classes: No suspicious classes found.
	IntCache: cache: 1, tcache: 24, allocated: 3, tallocated: 63
	Profiler Position: N/A (disabled)
	Vec3 Pool Size: 77 (4312 bytes; 0 MB) allocated, 77 (4312 bytes; 0 MB) used
	Player Count: 1 / 8; [jv['Player'/77, l='Demo_World', x=51,53, y=69,00, z=-386,85]]
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.