Fixed massCenter and massCenterW
Fixed massCenter and massCenterW

massCenter and massCenterW used GetMassCenter on the ent itself instead
of its phys object.
Also added a validity check to the retrieved phys objects.

Xandaros/Starfall,Jazzelhawk/Starfall,INPStarfall/Starfall,Xandaros/Starfall,Ingenious-Gaming/Starfall,Jazzelhawk/Starfall,Ingenious-Gaming/Starfall,INPStarfall/Starfall