Polar bears can crash the game.

When polar bears are angered by attacking a cub...

What I expected to happen was...:
The adults will all attack the player

What actually happened was...:
The game will crash, usually if there's more than a very small amount of adults nearby.

Steps to Reproduce:
1. In creative mode, spawn some polar bears, making sure there's at least 1 cub
2. Go into survival via commands
3. Attack the cub. The game will crash.