"save changed file" window displayed abnormally when closing Edi

[netflymachine]

When closing Edi after editing a text file without saving it, the background of "save changed file" window is abnormally black.

VS 2019 Community Version 16.11.3 (Edi successfully built)
Win10 20H2 19042.1237

Thank you ^.^

[netflymachine]

This happed when default theme "Metro Light" is used.
This issue is gone only when I changed the theme to "Generic".