Margin missing sometimes in the PR sidebar #4642

Please ensure:

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

Description

• May be related to https://github.com/sindresorhus/refined-github/issues/4638

Steps (it doesn't happen all the time, but reproducible enough)

1. Starting in a issue, like here (maybe refresh this page first)
2. Click the Pull requests tab (ajaxed)
3. Open a PR (ajaxed)
4. Notice the lack of margin in the sidebar:

   <img width="316" alt="Screen Shot 9" src="https://user-images.githubusercontent.com/1402241/128231003-0a8ce12a-11ce-4fca-89e0-e42b0c04de4a.png">

5. Refresh page
6. Notice it's fine

   <img width="307" alt="Screen Shot" src="https://user-images.githubusercontent.com/1402241/128231196-069ed856-bb99-4115-affe-a6bba8195544.png">

If it doesn't happen, just navigate between tabs and then enter a PR at last

Example URL

https://github.com/sindresorhus/refined-github/pull/4626 but starting from another page

Browser(s) used

Safari