elm/gengrid: more null checks for setting mirrored state during construction

Summary:
sd->obj is only non-null later in construction, so add even more checks for it
here

@fix
Depends on D8961

Reviewers: devilhorns

Reviewed By: devilhorns

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D8962

src/lib/elementary/elm_gengrid.c

@@ -3592,7 +3592,7 @@ _mirrored_set(Evas_Object *obj,
 
    ELM_GENGRID_DATA_GET(obj, sd);
 
-   if (efl_finalized_get(sd->obj))
+   if (sd->obj && efl_finalized_get(sd->obj))
      _item_cache_zero(sd);
    efl_ui_mirrored_set(efl_super(obj, MY_CLASS), rtl);