Plot zero when there is no data in line chart

I have a table of KPI cards and graphs on a report with each row for a different salesperson (see below). These are all really basic and I'm just using filters to get the data in each row for specific salespeople. One of the cards shows the count of proposals, but I can't use the filter on that card for a salesperson that has not generated any proposals because they aren't in the filter list. How do I force this to show zero?

I'm a complete newb, so I'm guessing there is a much better way to do this. 

Thanks!