BGE: Fix for #37335 "Moving the camera with a key (after the recent BGE cleanup commits) now crashes the game" reported by Ace Dragon.

CcdPhysicsEnvironment->GetCharacterController(); was missing a NULL check.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk@61174 954f8c5b-7b00-dc11-b283-0030488c597c