Scorecard Metric not Reading Zero values

Hi All,

I have a pie chart in our invoice management report which shows, of the unpaid invoices, the status as indicated by a document tag within our sharepoint library. In order to monitor the performance of reviewing the invoices as they come in I have a scorecard attached to the segment for 'New' items and data alerts and targets etc from that. 

Pie chart

The issue arises when all items have been reviewed, the segment is no longer visible in the pie chart and the metric returns a blank and remains at the previous value at the refresh before the blank. As the data alert usually spurs the team into action to review outstanding documents the same day, the following refresh usully indicates an erroneous high value as the zero cannot be recorded. 

Metric History

Is there a way to make the pie chart show zeros, or force the metric to reset to zero when no data is available?

I have seen some answers on here about making pie charts show zeros but as this is a count of text values in a cloumn none of those solutions have worked for me.