I have a course using the Multitopic course format. I just upgraded to Moodle 3.9+ and have the latest Multitopic plugin.
When I try to edit this course I cannot see the sub-topics and I get the following error message...
Exception - Class 'core_course\output\modchooser_item' not found
After a little exploring I realise that this relates to the theme. In the relevant directory (adaptable\classes\core_course\output, I believe, though I am working from memory here) there is a single file (modchooser.php) but I cannot see any actual class modchooser_item; though there is a reference to it.
Any ideas on this one?