Why can't I call the methods defined in system/library/cart.php from the controller files for the admin panel?
1) Trying to call $this->cart->clear(); from admin/controller/sale/order.php produces an error, as if the method didn't exist.
2) On the other hand $this->session->getId(); works fine when called from the same place.
3) When $this->cart->clear(); is called from catalog/controller/api/cart.php it works fine.
My OpenCart Version is 188.8.131.52.