Fixed USERADD_SYNC='boot,shutdownboot' registration

source/ubl-settings-usergroups.c

@@ -1057,7 +1057,7 @@ void on_expiration_clicked(GtkWidget *self, ubl_settings_usergroups_user_window
 			sync = "boot";
 		}
 		if (shutdown_active){
-			sync = yon_char_unite(sync,yon_char_is_empty(sync)?"":",","shutdown");
+			sync = yon_char_unite(sync,yon_char_is_empty(sync)?"":",","shutdown",NULL);
 		}
 		yon_config_register(USERADD_SYNC_parameter,USERADD_SYNC_parameter_command,sync);
 	}