Stolen from MDL-43016 as this is fixing a bug in the syntax of that fix.
Requires a site with several categories.
Log in as an admin
Turn on editing
Edit the navigation block settings
Turn on "Display categories as links" and save
Navigate to [Administration ► Site administration ► Courses ► Manage courses and categories]
Click on a category and "Courses" should appear in the navigation block.
Expand the "Courses" branch in the navigation.
Check that the course categories (loaded by AJAX) are links.