Background icon repeating in admin panel (Redmine 3.4.2)

[jmfarina]

In admin panel (/admin), the "Global hooks" and "Remote repository servers" buttons' icon is repeating itself with Redmine's default themes (and others as well, though I've seen at least one that works out of the box).
Adding the "icon" class to the a element fixes the problem:

<li><a class="icon global_hooks_label global-hooks" href="/hooks">Global hooks</a></li>
<li><a class="icon remote_repo_sites_label remote-repo-sites" href="/remote_repo_sites">Remote repository servers</a></li>