order_id is null in DB with Delivery Slots

Hi,

I m ussing your plugin Delivery Slots…the integration of it in the web site is successfu. But in DB table Delivery Slots the order_id is null ?!

I have checked the different files of the woocomerce and delivery Slots. How cant i fix this bug?! if i put the order id in this tab manually from the last command in panel admin , the data is recorded and the effects of this plugin are successful