Crash on coming closer to a high rate spawner

Put the summary of the bug you're having here

What I expected to happen was...:
Just to spawn potions into a specific place

What actually happened was...:
I came closer to the spawner, and the game crashed

Steps to Reproduce:
1. Generate any world
2. Make mortars with MCEdit filter Mortars by SethBling
3. Login to the world and go near the mortars