Navigation: add check that active.url actually exists

js/jquery.mobile.navigation.js

@@ -1116,7 +1116,7 @@ define( [
 			// However, if a dialog is already displayed at this point, and we're
 			// about to display another dialog, then we must add another hash and
 			// history entry on top so that one may navigate back to the original dialog
-			if ( active.url.indexOf( dialogHashKey ) > -1 && !$.mobile.activePage.is( ".ui-dialog" ) ) {
+			if ( active.url && active.url.indexOf( dialogHashKey ) > -1 && !$.mobile.activePage.is( ".ui-dialog" ) ) {
 				settings.changeHash = false;
 				alreadyThere = true;
 			}