[BUG] ShowPopupAsync deadlock when ShellNavigatingEventArgs is Cancelled

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Did you read the "Reporting a bug" section on Contributing file?

- [x] I have read the "Reporting a bug" section on Contributing file: https://github.com/CommunityToolkit/Maui/blob/main/CONTRIBUTING.md#reporting-a-bug

### Current Behavior

Calling Shell.Current.ShowPopupAsync() will hang indefinitely when ShellNavigatingEventArgs is cancelled.

Example
`
protected override void OnNavigating(ShellNavigatingEventArgs args)
{
args.Cancel();
}
`

### Expected Behavior

An Exception should be thrown.

### Steps To Reproduce

1) Override OnNavigating of Shell
2) Call Cancel on ShellNavigatingEventArgs
3) Hang forever

protected override void OnNavigating(ShellNavigatingEventArgs args)
{
args.Cancel();
}

### Link to public reproduction project repository

TODO

### Environment

```markdown
- .NET MAUI CommunityToolkit:
14.0.1
- OS:
Windows
- .NET MAUI:
10.0.41
```

### Anything else?

_No response_