BGE: Fix for [#34044] "Objects with no material don't have their "face image" always working on bge" reported by Dalai Felinto (dfelinto).

NULL materials are no longer cached.



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56680 954f8c5b-7b00-dc11-b283-0030488c597c