Filling in the HR1 Form (Home Rights) if you don't know the address of owner (Q7)

Following a separation, I am completing the HR1 form for our marital house which I still live in but the title deeds only list my husband's name. 

He has moved away and I don't have a forwarding address.  How do I complete question 7?  Can I leave it blank?  Should I try to track him down?  Thank you.

Sonja - panel 7 of form HR1 is for your (the applicant's) address so the one you want us to include on the register as part of the Notice entry