bug fix: fixed memory leak

Summary:
The original code created an edje object temporarily for index calculation
and didn't delete it which caused memory leak. fixed it.

Test Plan: None

Reviewers: Hermet, seoz

Reviewed By: Hermet

Differential Revision: https://phab.enlightenment.org/D246

legacy/elementary/src/lib/elm_index.c

@@ -228,6 +228,8 @@ _index_box_auto_fill(Evas_Object *obj,
 
         edje_object_size_min_restricted_calc(o, NULL, &mh, 0, 0);
 
+        evas_object_del(o);
+
         EINA_LIST_FOREACH(sd->items, l, it)
            if (it->level == level) num_of_items++;