void Stop()
 {
     windowController?.Close();
     uiController.Stop();
     disposables.Clear();
     uiController   = null;
     currentNavItem = -1;
     navStack.Clear();
 }
        void Stop()
        {
            if (uiController == null)
            {
                return;
            }

            DisableButtons();
            windowController?.Close();
            uiController.Stop();
            disposables.Clear();
            uiController   = null;
            currentNavItem = -1;
            navStack.Clear();
            UpdateToolbar();
        }