I've a problem with aggregates that return "not set" when they sum a value from cards but there are no cards that match the criteria.
Fore example I have an Epic which aggregates the "Story Point Estimates" of child stories. I want a value (if positive) of the difference between the estimate of the Epic and the sum of its children's estimates. Say the Epic's estimate is 80 and the sum of the children is 30, this indicates the team believe they will discover stories worth another 30 points before they're done. Adding the sum of the stories' estimates with these "remainders" will give us the current view of backlog size. Very helpful when breakdown of epics is going on in parallel with sprints.
Unfortunately in Mingle if the aggregate property does not find any cards in the set being added, the value returned for the aggregate is "not set". Differencing this in a formula property will also return "not set".
How can I get a zero in these circumstances rather than a null?