Description of the Issue

I have the latest version (Notepad++ v8.4.8) installed and now have dark mode.

Steps to Reproduce the Issue

1. Start in light mode with a file open.
2. Switch to dark mode.
3. Switch back to light mode.
4. A black vertical bar now appears on the left of the text; to the right of the row counter ruler.

Expected Behavior

That bar should not be there.

Actual Behavior

Debug Information