filter-comments-by-you not displayed any more on PR list page

[arnaudvalle]

(Note: Initially reported as part of #2631 but they're two different issues)

Example url: https://github.com/sindresorhus/refined-github/pulls?q=is%3Apr+is%3Aopen+sort%3Aupdated-desc

1. The link Everything commented by you added by the filter-comments-by-you is not showing up anymore.
2. The icon of the button seems misaligned. (separate issue Filters selection box on issues page is blank #2651)

content.js:2997 TypeError: Cannot read property 'before' of null
    at filter_comments_by_you_init (content.js:5257)
    at features_run (content.js:2992)
    at content.js:3039
    at content.js:2949

[GF-Huang]

The problem arises again.

[fregante]

The feature works, the item has just been changed to "involved in"