elm_config: Avoid access of deleted item data.

This belongs to the fixes raster just did here. It was the only one I was able
to trigger after his fixes.

Last one in a row that fixes T2072.

legacy/elementary/src/bin/config.c

@@ -2025,6 +2025,7 @@ _font_classes_list_sel(void *data   EINA_UNUSED,
         const char *s;
 
         s = elm_object_item_text_get(list_it);
+        if (!s) continue;
 
         if (tc_data->font && !strcmp(s, tc_data->font))
           {