Put the summary of the bug you're having here

What I expected to happen was...:
the horse should've died, neither of us spawned the wither.

What actually happened was...:
the animal went through the wall, a wither spawned out of NOWHERE, it won't let me tame animals
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ... build a pen with a wood and glass wall behind it
spawn horse or animal, punch it.
this was on 1.8.3 but its not on here.