Description
If I open a file from disk and have an unsaved tab open at the same time, clicking the unsaved tab's "x" while in the from-disk tab closes the unsaved tab without asking if I want to save. It doesn't matter if I open the file first and then make a new tab or make a new tab and then open a file.

To Reproduce

1. Launch PTE.
2. Create a new document.
3. Edit the new document.
4. Open an existing file from disk (I've specifically done this with a GP5 and PT2 file).
5. While in the opened file tab, click the "x" on the Untitled tab.
6. Untitled tab closes without the dialog asking if I want to save the modified file.

Version
I'm running in macOS 10.15.5 and Alpha 13 of PTE.