Avoid errors caused by more-dropdown on issues

[yakov116]

1. LINKED ISSUES:
   Fixes GetCurrentBranch Stopped working on issues #3641

2. TEST URLS:
   GetCurrentBranch Stopped working on issues #3641

3. SCREENSHOT:
   None

[yakov116]

@fregante when you approve can I assume the title is good?

[yakov116]

https://github.com/sindresorhus/refined-github/blob/10dc4ac56c299c011733483a20725f3618a05175/source/github-helpers/github-url.ts#L65

Here is the issue

[fregante]

Just fix the type issue with ! or something.

I checked all the features where we use GitHubURL and all of them have a branch. In forked-to we specifically avoid errors by limiting the usage of GitHubURL to pages with a branch, even if the feature is enabled on isRepo https://github.com/sindresorhus/refined-github/blob/d7d700a20befb552f9f64e15504b845dbe04e699/source/features/forked-to.tsx#L34-L36

In another feature we also specifically mention the incompatibility so we don't use GitHubURL:
https://github.com/sindresorhus/refined-github/blob/b7d31c6ae88ce48f4f5fa2716716a40e32eeea1b/source/features/comments-time-machine-links.tsx#L77

[fregante]

@fregante when you approve can I assume the title is good?

Not always. Generally try to make the commit titles readable by users. "returns undefined" doesn't explain how this helps the user. In this case the specific user-facing bug being solved is Avoid errors caused by `more-dropdown` on issues or Fix XYZ link in `more-dropdown` on issues or something along those lines