Changing a null BAQ output total value to a zero

I have a BAQ that summarizes the total quantity on hand for parts across all warehouses. If there isn't a PartWhse record found for a part the BAQ returns a null value for the total on hand calculated field.

Here is the syntax used for the calcualtion for the total on hand.
TOTAL (PartWhse.OnHandQty)

How can I format the 4GL code to change a null value to a zero?

Thank in advance.