If you are using an operator that is going to sum the value from a list of things, and that list of things is empty (for example a field that is a list of related items, and the field is empty) should the sum operator return an empty value or should the sum return a value of 0?
I would imagine that it should return a value of 0 rather than empty because if we have a field that is a number and the value is empty, no operators will work properly.
