Register domain using only 1 DNS

[d4rkr3pt0r]

Hi

I'm developing a registrar module. This is what happens when users enter no DNS or only one DNS during domain registration proccess:

When no DNS has entered: Whmcs sends default DNS to registrar module.

When only one DNS has entered: Whmcs wont send register domain command to  the registrar module. (Order would place with "pending status").

When 2 or more DNS has entered : Everything works fine.

What is the problem?

I need to register domain without any name server when none of DNS fields are filled and also with only one dns when only one DNS has filled.

Thanks