Fix Face Set overlay rendering wrong color with modifiers

face_set_color_default was not copied when copying meshes, so when
extracting the colors in the draw cache it was using a wrong default
color ID.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D8957

source/blender/blenkernel/intern/mesh.c

@@ -927,6 +927,7 @@ void BKE_mesh_copy_settings(Mesh *me_dst, const Mesh *me_src)
   me_dst->remesh_mode = me_src->remesh_mode;
 
   me_dst->face_sets_color_seed = me_src->face_sets_color_seed;
+  me_dst->face_sets_color_default = me_src->face_sets_color_default;
 
   /* Copy texture space. */
   me_dst->texflag = me_src->texflag;