When a user has grades for a course they're no longer enrolled in, these won't be displayed properly on the grades screen.

This is happening because two endpoints are being called to retrieve this information. The first one gets all of the user grades, whilst the second one is only retrieving information for enrolled courses.

This can be fixed by calling the core_course_get_courses_by_field endpoint instead. But this may not be available for old versions. So it should fall back to using the current implementation but cleaning up missing grades.