Blender Git Loki

Fix segfaults when deleting objects with upstream bullet lib

Blender tried to free objects twice from the bullet world sometime.

First we would implicity remove all objects when recreating the bullet
world and then explicity try to remove them again from the now empty
world.

This would wouldn't crash older bullet versions, but the recent versions
will as we will try to free objects that no longer exists in the bullet
world.

Also clear the cache on deletion as the object order changes.
Fix T77181: The cache clearing will fix this issue.