Comment 4 for bug 1242801

With further debugging, the direct reason seems to be a "notify::popup-shown" signal being emit and changes the stamp in GtkTreeModelFilter in the path: combo_box_notify_popup_shown_cb -> gtk_tree_model_filter_refilter -> gtk_tree_model_foreach -> gtk_tree_model_filter_refilter_helper -> gtk_tree_model_filter_row_changed -> gtk_tree_model_filter_increment_stamp

Not sure what is the real reason but setting the stamp back after this prevent the segfault.