Navigation between commits with shortcuts x and c do not work anymore

Summary

When reviewing a Merge Request, the navigation keyboards shortcuts to switch between commits (shortcuts x and c) do not have any effect

Steps to reproduce

Open a merge request with multiple commits
Click on one commit link to see its specific diff
Click on keyboard keys c or x to navigate

Example Project

Reproduced on every Gitlab projects:

For instance: https://gitlab.com/gitlab-org/gitlab (Gitlab)

Seems similar on open or closed Merge request, for instance (chosen at random) this merge request: !168420 (8e371198)

What is the current bug behavior?

Nothing happens, the page is stuck on the currently selected commit

What is the expected correct behavior?

Navigate to next or previous commit of the MR

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of: \\\`sudo gitlab-rake gitlab:env:info\\\`) (For installations from source run and paste the output of: \\\`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production\\\`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of: \`sudo gitlab-rake gitlab:check SANITIZE=true\`) (For installations from source run and paste the output of: \`sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true\`) (we will only investigate if the tests are passing)