Action addLineItemDiscount doesnt exists

There is a call from ajax function (commerce_pos_discount_commerce_pos_sale_form_ajax_alter) to add new discount via ajax (call to current transaction and call action addLineItemDiscount).

The problem is that the action addLineItemDiscount does no exist on the module so the system send an error.

I am not sure if I am doing something wrong so sorry!, just in case :D