Datapoint expression for widgets similar to un() when no active instances

We'd like to see a datapoint expression for widgets similar to the un() expression which returns a value when there are no active instances, rather than throwing an error. For example if I create an aggregated datapoint to sum all Netapp volumes containing "_ABC_" but there are no volumes that match this the graph throws an error that there are no active instances. It would be useful if we had an expression that could return a value instead of creating an error, ex. if(noInstances(ABC_Volumes),0,ABC_Volumes).