When the world is being closed or saves during gameplay the game freezes. for the duration of the world being saved.

What I expected to happen was...:
World would contnue to to operate smoothly

What actually happened was...:
game freezes, new terrain doesnt load, animals freeze in place, blocks that are broken reappear and dont drop anything, damage isnt applied etc.

Steps to Reproduce:
1. Play the game and wait for the world to start saving, Best visible when you have a pet.
2. Game freezes