Hiding null in bar chart legend when using a master calendar

Hi,

This is a feature request in response to https://community.vizlib.com/helpdesk/tickets/19614

The issue is that NULL is displayed in the bar chart legend when a user wants to display all months using a master calendar.  The only way currently to hide the NULL is to untick the "Include null values" option but this has the undesired effect of hiding the month with no value which prevents a consumer of the dashboard to be unable to identify e.g, a month where there are no sales. 

Cheers

Joel