I used MCedit with an NBTedit filter to change Donkey with chest to Horse or Donkey with chest to an Undead Variation. Though when attempting to open the horses UI while in-game, I crashed.

Not sure how long its been like this, 13w22a is the first snapshot i've tried this in.

What I expected to happen was...:
To be able to open the inventories of the Horses and Undead Variations.

What actually happened was...:
I crashed upon attempting to open Horse UI

Steps to Reproduce:
1. Spawn a Donkey and add a chest to it.
2. Open an NBTeditor or MCedit with a NBTedit filter to change Donkey to either a Horse or its Undead Variation.
3. Attempt to open Horse UI in-game.