`filter-comments-by-you` not displayed any more on PR list page #2647

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(Note: Initially reported as part of https://github.com/sindresorhus/refined-github/issues/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 https://github.com/sindresorhus/refined-github/issues/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