The game crashes when a tamed wolf kills a mob

A baby-zombie hitted me so my wolfes start killing him and the moment he died my game died too. The same happend with a sheep.

What I expected to happen was...:
The wolves would kill the zombie and the game won't crash

What actually happened was...:
The wolves killed the zombie and the game crashed

Steps to Reproduce:
1. Find a wolf and tame it
2. Order it to attack a mob
3. Watch as the moment he kills it the game crashes