Fix #108266: sculpt auto created color attribute not set as render color

When entering sculpt mode on an object without any color attributes and
starting to paint, the newly created color attribute was set active, but
not default (camera icon).

Now set it default as well.

Pull Request: https://projects.blender.org/blender/blender/pulls/108271

source/blender/blenkernel/intern/paint.cc

@@ -1936,6 +1936,7 @@ void BKE_sculpt_color_layer_create_if_needed(Object *object)
   }
 
   BKE_id_attributes_active_color_set(&orig_me->id, unique_name);
+  BKE_id_attributes_default_color_set(&orig_me->id, unique_name);
   DEG_id_tag_update(&orig_me->id, ID_RECALC_GEOMETRY_ALL_MODES);
   BKE_mesh_tessface_clear(orig_me);