`edit-comments-faster` is failing on locked issues #4031

Visit: https://github.com/sindresorhus/refined-github/pull/4030 (as a collaborator)

Or any locked issues/PRs on repositories you control.

This is because we use the Add Reaction button as an anchor to append the button, but it doesn't exist.

Notice:

• No "fast edit" button
• Console error:

      Uncaught TypeError: Cannot read property 'after' of null
          at add (chrome-extension://idimlddndkhicdpjaoncjcgejgbmhogm/build/refined-github.js:3165)
          at runAdd (chrome-extension://idimlddndkhicdpjaoncjcgejgbmhogm/build/refined-github.js:17529)
          at applyChanges (chrome-extension://idimlddndkhicdpjaoncjcgejgbmhogm/build/refined-github.js:17445)
          at SelectorObserver.addRootNodes (chrome-extension://idimlddndkhicdpjaoncjcgejgbmhogm/build/refined-github.js:17965)
          at Array.processBatchQueue (chrome-extension://idimlddndkhicdpjaoncjcgejgbmhogm/build/refined-github.js:17386)
          at MutationObserver.handleMutations (chrome-extension://idimlddndkhicdpjaoncjcgejgbmhogm/build/refined-github.js:17420)

You should be able to see the Edit button on this comment:

<img width="206" alt="Screen Shot" src="https://user-images.githubusercontent.com/1402241/109399226-32dcdf80-7907-11eb-8f6c-dfc5e4485a26.png">