Properly fix T45477

Code was actually skipping setting color selection indices and previous
commit actually broke mask selection in texture painting.
All should work now.

source/blender/blenkernel/BKE_DerivedMesh.h

@@ -150,6 +150,7 @@ typedef enum DMDrawFlag {
 	DM_DRAW_USE_ACTIVE_UV       = (1 << 2),
 	DM_DRAW_USE_TEXPAINT_UV     = (1 << 3),
 	DM_DRAW_SKIP_HIDDEN         = (1 << 4),
+	DM_DRAW_SKIP_SELECT         = (1 << 5),
 } DMDrawFlag;
 
 typedef enum DMForeachFlag {