#55 Meshes on a billboard prim causes bug in material changing

[Ali Kämäräinen]

Combining billboard feature and 3D mesh causes bug in material changing when the mesh is set to none. Material is changable when mesh is used again though.

Steps to repro:
-Build a new prim
-choose reX panel
-enable Extented properties
-ennable Billboard feature
-choose a mesh
-set mesh to none
-try to change the material