Folder tree has unlabeled links:
<a href="#" class="ygtvspacer"> </a>
This link should have text content. Alternatively, they should have aria-label attribute.
As far as I can see, these links are added in lib/yuilib/2in3/2.9.0/build/yui2-treeview/yui2-treeview* files. Not sure how to fix it, since this library (YUI2) has been deprecated since 2011 as far as I know.