query_objects sort did not exclude objects with an unset date field

The man page says "Objects with no stored value for the sort field are EXCLUDED from sorted results", but sort="dueDate asc" on TaskTracker.TaskTrackerClass returned all three objects with dueDate: (unset). The response also lacked its footer line.

Expected: Either zero results (per the documented rule) or the rule reworded (e.g. "objects with no property row for the field are excluded; a stored empty value counts as present, sorts first and displays as (unset)"). The footer ("Found N matching objects...") should be present.

Actual: Three results, no footer.