Right-clicking an empty `TextBox` briefly flickers `TextCommandBarFlyout`

### Describe the bug

When right-clicking an empty `TextBox` in WinUI (while having nothing in clipboard), the flyout of the `TextBox` briefly flickers on screen and disappears:

https://github.com/user-attachments/assets/ec2251ee-0ef6-4f68-a34f-df863f74bb3d

### Why is this important?

It is an odd behavior which is not expected by users.

### Steps to reproduce the bug

1. Open WinUI Gallery and navigate to `TextBox` sample
2. Right-click the empty `TextBox`
3. **Notice the behavior described above**

### Actual behavior

See video above

### Expected behavior

No context menu should appear

### Screenshots

_No response_

### NuGet package version

None

### Windows version

_No response_

### Additional context

_No response_

Reproduce the issue in the WinUI Gallery TextBox sample by right-clicking an empty TextBox with an empty clipboard. Start by tracing the TextBox context-menu behavior involving TextCommandBarFlyout; done means the flyout no longer briefly appears in this scenario and the relevant behavior is covered by an appropriate test.

Written by the indexing model from the issue text.