Can't delete course category

Navigate to Courses > Manage courses and categories Create two new categories as top-level categories: Category 2 Category 3 Create a new course in existing Category 1 Delete Category 1 Set What to do field to Move contents to another category Clear the Move into field Press Delete Confirm you see a "Required" error next to Move into field Set Move into to Category 2 Press Delete Confirm category was deleted; course was moved to Category 2 Delete Category 2 Clear the Move into field Set What to do field to Delete all - cannot be undone Press Delete Confirm course was deleted Confirm category was deleted