Fixes division by zero when 3d body does not have valid shape (3.2 only) 
Fixes division by zero when 3d body does not have valid shape (3.2 only) 

Fixes #46738 by setting the default inertia to a valid value when there are no valid shapes for a 3d body.
ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot