rem: if ( ! iface )
add: tree_view = g_object_get_data ( G_OBJECT(model), "tree-view" ); if ( !iface || !tree_view )
context: void appui_sur_ajout_division ( GtkTreeModel * model ){    MetatreeInterface * iface;    GtkTreeIter iter, sub_iter;    gint div_id;    iface = g_object_get_data ( G_OBJECT(model), "metatree-interface" );       if ( ! iface )	return;    div_id = iface -> add_div ();    gtk_tree_store_append ( GTK_TREE_STORE(model), &iter, NULL );    fill_division_row ( model, iface, &iter, iface -> get_div_pointer ( div_id ) );        gtk_tree_store_append (GTK_TREE_STORE (model), &sub_iter, &iter);    fill_sub_division_row ( GTK_TREE_MODEL(model), iface, &sub_iter, 			    iface -> get_div_pointer ( div_id ), NULL );    modification_fichier ( TRUE );}