Crash: Tesselating block in world java.util.ConcurrentModificationException

---- Minecraft Crash Report ----
// Why is it breaking :(

Time: 23.07.14 22:35
Description: Tesselating block in world

java.util.ConcurrentModificationException
	at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at chc.b(SourceFile:302)
	at chc.a(SourceFile:281)
	at cjr.a(SourceFile:118)
	at cjq.a(SourceFile:67)
	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$Itr.checkForComodification(Unknown Source)
	at java.util.ArrayList$Itr.next(Unknown Source)
	at chc.b(SourceFile:302)
	at chc.a(SourceFile:281)
	at cjr.a(SourceFile:118)

-- Block being tesselated --
Details:
	Block type: ID #9 (tile.water // azp)
	Block data value: 0 / 0x0 / 0b0000
	Block location: World: (86,62,264), Chunk: (at 6,3,8 in 5,16; contains blocks 80,0,256 to 95,255,271), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Stacktrace:
	at cjq.a(SourceFile:67)
	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 (amd64) version 6.1
	Java Version: 1.8.0_05, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 336758992 bytes (321 MB) / 522190848 bytes (498 MB) up to 954728448 bytes (910 MB)
	JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G
	IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95