Stop #DIV/0! From Appearing

Please see attached example

I realize that this is probably simple fix but for some reason it's giving me trouble. I don't have any issue with #DIV/0! showing up in the Data sheet, but I need to know how to go about having it not appear on the Scorecard sheet. Not only does it look bad but it hinders the Year to Date Average from automatically tallying up each month. Any help would be most appreciated. Thank you!