`git-checkout-pr` is missing in some cases #4489

The sidebar overlap is tracked in #4490

Missing from https://github.com/sindresorhus/refined-github/pull/4395

<img width="511" alt="Screen Shot 16" src="https://user-images.githubusercontent.com/1402241/122522705-72f3d980-d040-11eb-9726-448ff38fff95.png">

Present in https://github.com/twbs/bootstrap/pull/30329

<img width="449" alt="Screen Shot 17" src="https://user-images.githubusercontent.com/1402241/122522742-7d15d800-d040-11eb-8c92-257a1d2808f1.png">

Probable error:

<img width="745" alt="Screen Shot 18" src="https://user-images.githubusercontent.com/1402241/122522835-94ed5c00-d040-11eb-8d88-0f298af6d673.png">