[Bug]Cannot drag and move the window, if there is an modal of tips to save the change when you click close

Describe the bug Cannot move the window, if there is an modal of tips to save the change. If the modal is not visible, you can only use the escape key to close the modal box, and then drag and move the window, then close the windows and click "Discard & Exit".

To Reproduce Just open notepads and type some word, then click close.

Expected behavior The window should can be dragged as another UWP app like "Paint 3D" when it exists a modal.

Screenshots (a 10M gif screenshots, playback in browser may be slow)

Desktop:

• OS: Windows 10 2004 19041.487
• Version v1.4.2.0

Additional context This issue may like #678