mycelium crash

when I go around in my world, the game crashes when spectating and going trough the mycelium ground

report:

---- Minecraft Crash Report ----
// Don't do that.

Time: 23-7-14 17:50
Description: Tesselating block model

java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
	at java.util.ArrayList.rangeCheck(Unknown Source)
	at java.util.ArrayList.get(Unknown Source)
	at csu.b(SourceFile:88)
	at chc.a(SourceFile:156)
	at cjs.a(SourceFile:139)
	at cjs.a(SourceFile:74)
	at cjs.a(SourceFile:43)
	at cjs.a(SourceFile:35)
	at cjq.a(SourceFile:62)
	at cmt.b(SourceFile:156)
	at cmm.a(SourceFile:71)
	at cmm.run(SourceFile:31)
	at java.lang.Thread.run(Unknown Source)


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

-- Head --
Stacktrace:
	at java.util.ArrayList.rangeCheck(Unknown Source)
	at java.util.ArrayList.get(Unknown Source)
	at csu.b(SourceFile:88)
	at chc.a(SourceFile:156)
	at cjs.a(SourceFile:139)
	at cjs.a(SourceFile:74)

-- Block model being tesselated --
Details:
	Block: minecraft:mycelium[snowy=false]
	Block location: World: (147,54,642), Chunk: (at 3,3,2 in 9,40; contains blocks 144,0,640 to 159,255,655), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
	Using AO: true
Stacktrace:
	at cjs.a(SourceFile:43)
	at cjs.a(SourceFile:35)

-- Block being tesselated --
Details:
	Block type: ID #110 (tile.mycel // awy)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (147,54,642), Chunk: (at 3,3,2 in 9,40; contains blocks 144,0,640 to 159,255,655), Region: (0,1; contains chunks 0,32 to 31,63, blocks 0,0,512 to 511,255,1023)
Stacktrace:
	at cjq.a(SourceFile:62)
	at cmt.b(SourceFile:156)
	at cmm.a(SourceFile:71)
	at cmm.run(SourceFile:31)
	at java.lang.Thread.run(Unknown Source)

-- System Details --
Details:
	Minecraft Version: 14w30b
	Operating System: Windows 7 (x86) version 6.1
	Java Version: 1.7.0_65, Oracle Corporation
	Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
	Memory: 187909368 bytes (179 MB) / 518979584 bytes (494 MB) up to 518979584 bytes (494 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
	IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0