add: if ( ! date_b ) return 1; if ( ! date_a ) return -1;
context: inline gboolean metatree_sort_column  ( GtkTreeModel * model, 					GtkTreeIter * a, GtkTreeIter * b, 					gpointer user_data ){    GDate * date_a = NULL, * date_b = NULL;    gchar * string_a, * string_b;    gtk_tree_model_get ( model, a, 			 META_TREE_DATE_COLUMN, &date_a, 			 META_TREE_TEXT_COLUMN, &string_a,  -1 );    gtk_tree_model_get ( model, b, 			 META_TREE_DATE_COLUMN, &date_b, 			 META_TREE_TEXT_COLUMN, &string_b, -1 );    if ( date_a && date_b )    {	return g_date_compare ( date_a, date_b );    }        return g_utf8_collate ( string_a, string_b );}