On the page /local/moyclass/index.php when using Moodle 4.3 I see this error.
Manage ForClasses
Exception - local_moyclass\api_service::get_lessons(): Return value must be of type array, null returned
Debug info:
Error code: generalexceptionmessageDismiss this notification
Stack trace:
line 123 of \local\moyclass\classes\api_service.php: TypeError thrown
line 241 of \local\moyclass\classes\manager_db.php: call to local_moyclass\api_service->get_lessons()
line 43 of \local\moyclass\classes\pages\dashboard.php: call to local_moyclass\manager_db->set_lessons()
line 41 of \local\moyclass\index.php: call to local_moyclass\pages\dashboard->render()
PS. Yes, there are some non-Russian schools using MoyKlass :)