Could a BeginInvokeOnMainThread method be looping and causing a memory leak?

I have an application that works but after a while when I debug on my iPhone it hangs the phone and the only way I can recover is a hard reset of the button on the side and the home button.

First of all, could that be because my application has a memory leak?

Here's the code for the application. In particular, I am looking at the BeginInvokeOnMainThread method. Can someone tell me if they can see if there could be any problems with the way that it is implemented? Also, what's the purpose of the .ContinueWith((arg).

namespace Japanese
{
    public partial class PhrasesFrame : Frame
    {

        CancellationTokenSource cts = new CancellationTokenSource();

        public PhrasesFrame(PhrasesPage phrasesPage)
        {
            InitializeComponent();
            this.phrasesPage = phrasesPage;
            AS.phrasesFrame = this;
            Device.BeginInvokeOnMainThread(() => ShowCards(cts.Token).ContinueWith((arg) => { }));
        }

        public void Disappearing()
        {
            cts.Cancel();
        }

        public async Task ShowCards(CancellationToken ct)
        {
            AS.cardCountForSelectedCategories = App.DB.GetCardCountForSelectedCategories();
            while (!ct.IsCancellationRequested)
            {

                await Task.Delay(500);
            }
        }
    }
}