Put the summary of the bug you're having here

What I expected to happen was...:

After dismounting the horse, for the horse to walk away.

What actually happened was...:

Occasionally, the horse will dissappear. It will still make sound effects, such as grunting, sighing or neighing, but the horse can't be seen nor interacted with. You can fix this by exiting the world and loading it back up. 

Steps to Reproduce:
1. Crate a normal world, not superflat.
2. Either spawn in or find a horse, tame it and put a saddle on it.
3. Sprit around for a while on the horse, then dismount. As this bug only happens occasionally it may take a few tries.