title: InvalidCastException on ShareTarget [Windows 10 UWP]
body: <p>I have app that supports ShareTarget to upload files to cloud. Everything works great when I my app is closed (and I mean closed - not hibernated or something like this) - I choose share photo and everyting goes as expected. But when I open the app, then exit (app stays hibernated in memory) and try to share something on line </p>
  
  <pre><code>Window.Current.Activate();
  </code></pre>
  
  <p>I get </p>
  
  <pre><code>Exception thrown: 'System.InvalidCastException' in mscorlib.ni.dll
  Message "Unable to cast COM object of type 'System.ComponentModel.PropertyChangedEventHandler' to class type 'System.ComponentModel.PropertyChangedEventHandler'. Instances of types that represent COM components cannot be cast to types that do not represent COM components; however they can be cast to interfaces as long as the underlying COM component supports QueryInterface calls for the IID of the interface."
  </code></pre>
  
  <p>Then my app closes completely and second try is success. Whole onShareTarget code:</p>
  
  <pre><code>protected override void OnShareTargetActivated(ShareTargetActivatedEventArgs args)
  {
      if (!args.ShareOperation.Data.Contains(
          Windows.ApplicationModel.DataTransfer.StandardDataFormats.StorageItems))
          return;
      AppShell shell = Window.Current.Content as AppShell;
      if (shell == null)
          shell = new AppShell();
      Window.Current.Content = shell;
      shell.AppFrame.Navigate(typeof(ChooseFolderPage), args.ShareOperation);
      Window.Current.Activate();
  }
  </code></pre>
  
  <p>Any ideas how to fix it?</p>