Minecraft crashes upon opening a commandblock

In 14w08a i just discovered a bug whereby Minecraft crashes when i opened a commandblock.

I'm not sure how to recreate this bug or if it actually is linked to commandblocks, but this is what happened:
I was playing around with commandblocks set to a command like

/clone 1112 0 112 1117 21 122 ~-2 ~-12 ~-5 replace

i selected a region bigger than 4096 blocks total so i split up the clone command into two commandblocks.

after i did that the some parts of commandblocks began to shift and various other commandblocks got triggered, so i can't really tell whether it is the /clone command, the /tp command, the /testfor with a target with rx, rxm, ry and rym, or if it even is a command inflicting it.

after this i just tried to open a commandblock to fix it and the game just crashed.

I've put a crash report in the attachement if you would need it.
To me the crash report looks really short actually and its nothing I really understand.

I don't think this has too high of a priority because to me the crash sounds kind of random and after I tried to recreate it nothing really happened.

Description: Unexpected error

java.lang.ClassCastException: arn cannot be cast to arl
	at ame.a(SourceFile:66)
	at bon.a(SourceFile:279)
	at bdq.aj(SourceFile:1246)
	at bdq.p(SourceFile:1590)
	at bdq.ah(SourceFile:791)
	at bdq.f(SourceFile:745)
	at net.minecraft.client.main.Main.main(SourceFile:121)