Fix #35480: object without material crash blender when starting game engine

Was a missing NULL-pointer check. No idea why it took so long to figure
issue out -- apparently there was no crash in linux for me and msvc
didn't show any backtrace :S

Also corrected weirdo way of bit flag check which was:
  !ma->mode & MA_FACETEXTURE
better do !(ma->mode & MA_FACETEXTURE) since ! is a logic NOT.

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@57052 954f8c5b-7b00-dc11-b283-0030488c597c