When choosing Course Overview report from Settings -> Reports -> Course Overview, no chart is displayed and broken image link is shown instead. When choosing to show image in new tab the following error is displayed:

Notice: Undefined variable: params in /moodle/admin/report/courseoverview/reportsgraph.php on line 30

Fatal error: Cannot access empty property in /moodle/admin/report/courseoverview/reportsgraph.php on line 30