BGE: Fix for [#35320] "Crash When Adding Property without Setting Material" reported by Leon Cheung.

Adding an extra NULL check to draw_mesh_text() to avoid accessing a NULL material array.



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56745 954f8c5b-7b00-dc11-b283-0030488c597c