Fix T41532: Some files bounce back and forth between 'packing BVH nodes' and 'Copying Transforms to Device'

This was originally caused by a6ae12a where i didn't foresee unclear distinguishing
between empty and non-synced meshes will give issues for the viewport. They're the
same for final rendering, but for viewport we need to be accurate here.

intern/cycles/render/mesh.h

@@ -71,6 +71,9 @@ public:
 	ustring name;
 
 	/* Mesh Data */
+	bool geometry_synced;  /* used to distinguish meshes with no verts
+	                          and meshed for which geometry is not created */
+
 	vector<float3> verts;
 	vector<Triangle> triangles;
 	vector<uint> shader;