Array to string conversion in DB_DataObject when doing on behalf of and no state/province

If you submit a contribution on behalf of an org and leave the state/province blank, you get Notice: Array to string conversion in DB_DataObject->_build_condition() (line 2903 of .../web/sites/all/modules/civicrm/packages/DB/DataObject.php)

(At the moment to see this you need to make the field not required on the profile, but it happens either way it's just there's currently a separate issue when the field is required and the country has no state/provinces.)

What happens is that at that code line $this->name and $this->abbreviation contain a big long list of numbers and letters, including, oddly, the strings "_A", "_B", "_C", etc, but ONLY up to "_P".