Put the summary of the bug you're having here
What I expected to happen was...:
The spawner to be created and it to spawn mobs as normal
What actually happened was...:
When I entered the world the game crashed
Steps to Reproduce:
1. Spawn a mob in game
2. use a third party tool like mcedit to make a spawner
3. enter the world
Duplicate of MC-16290, please use the search function to see if your bug has already been submitted. Currently over 56% of tickets are being closed as duplicate.