GitHub changed the style
Demo page: https://github.com/babel/babel/commits/master?after=ddd40bf5c7ad8565fc990f26142f85613958a329+104


Uncaught (in promise) TypeError: Cannot read property 'prepend' of null
at mark_merge_commits_in_list (content.js:1952)
at enableFeature (content.js:816)
at <anonymous>
As always, this change hasn't happened to GHE yet, please keep that in mind when fixing it. :)
Most helpful comment
Related: https://github.com/blog/2496-commit-together-with-co-authors