If I /give myself a player head with SkullOwner set to "MHF_<some name>" and try to place it, the game freezes for approx. half a second, then the world saves and then the game crashes. Log files tell that there happens a NullPointerException.

After loading the world again, the head is there with intended skin and everything is ok.

I didn't make any kind of research with different setups, so that's all I know. :/ Check the log file that I attached for more info.