File list has extra border when toggled off with `toggle-files-button` #4719

Please ensure:

• The bug is caused by Refined GitHub. It doesn't happen if I disable the extension.

Description

GitHub recently changed some styles (seems to be for logged-in users only, possibly related to https://github.blog/changelog/2021-08-25-dark-high-contrast-theme-ga/) and I noticed the file list has extra bottom border after toggling it off with toggle-files-button.

Screenshot

It seems the old style has this bug too:

Console errors

No response

Example URL

https://github.com/sindresorhus/refined-github

Browser(s) used

Chrome