Blender Git Loki

Fix for setting uv_layer name for modifiers

Issue was caused by missing fdata for meshes which doesn't have tessellated
faces yet. Real fix would be to use loop's MLOOPUV layer, but currently interface
is using mtex layer names for UV lists so use poly's mtex layer to check if
layer name is indeed correct.
Should work fine until we'll separate setting textures and UV coordinates.