Minecraft world crashes on start

Put the summary of the bug you're having here

What I expected to happen was...:
Load a world

What actually happened was...:
Minecraft Crashed

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How To Create Problem
1. Create a world
3. Close Minecraft (or go to Title screen)
4. Open MCEdit for 1.5.2
5. Open your created world
6 Use the Stack Entities Filter to stack anything on a Horse
7. Close MCEdit
8. Open your world in Minecraft
9. CRASH