Resolve model has nullable field

[Chukwunonso Nwankpa]

Hi
I am currently new to django and working on a directory project.
I recently setup a review model to another model in my app

But when I post the review it returns an integrity error saying a column contains null values
Please how do I resolve this.

Your help would much appreciated.

Chukwunonso Nwankpa
Plot 13 Benson .O. Nwanjoku Street,
Thinkers Corner,
Emene, Enugu,
Enugu State,
South East Nigeria.