I was in the new End dimension (not sure what it is being called) and I placed down a wither skull, I mine it back, and I crash. I haven't tested this with other heads, because I crashed, but I would assume they would all do this since they are basically the same thing with different textures.
Edit: Also not sure if this happens in every dimension or not, again, I haven't gotten back on yet. Yes, I'm making this very prematurely without thinking twice about it, sorry.

Crash Report: http://pastebin.com/iXZYWe1d