Sending Coupon Code Error and Some advise

[pjwebmaster]

I want to send the coupon code to all subscriber but there's an error when i try to, it say

Technical problem
Sorry, but the action you requested cannot be completed at this time because of a technical problem. We apologize for the inconvenience.

(1048) Column 'user_id' cannot be null in query

How can i fix this problem???

Also i tried to integrate the payment of a business directory site with Delavo. How can i do that? Please advise

Thanks,