Nested dialog not visible after closing and reopening parent dialog #3735

Bug explanation

When you close a parent dialog which has a nested dialog open, the nested dialog becomes invisible the next time you open the parent dialog, it prevents all input because only the nested dialog PART_ContentCoverGrid is visible:

This seems to work fine with TransitionAssist.DisableTransitions="True":

Steps:

• Open Root dialog
• Root dialog opens Inner dialog
• Close Root dialog
• Reopen Root dialog

    public RootDialog RootDialog { get; } = new();

    public MainWindow()
    {
        InitializeComponent();

        _ = Application.Current.Dispatcher.InvokeAsync(async () =>
        {
            await Delay();
            _ = DialogHost.Show(RootDialog);
            await Delay();
            RootDialog.OpenInnerDialog();
            await Delay();

            DialogHost.GetDialogSession(null)!.Close();

            await Delay();
            _ = DialogHost.Show(RootDialog);
        });

        static Task Delay() => Task.Delay(2000);
    }

I'm not sure if this is even desired behavior, I assumed that all nested dialogs would close when parent is closed.
Hope I described the issue clearly, its a little bit hard to explain.

Version

5.1.0