Saving a contact with a null County/StateProvince with Google geocoding gives an error.

In the UK, Royal Mail no longer used county names in addresses.  Thus the County field is redundant and not all contacts have them.  However, when you save such a contact you get an error.  I've done some investigation and may propose a fix, but think the issue needs to be flagged in case someone else already has a fix.

The issues seems to be in line 85 of  /administrator/components/com_civicrm/civicrm/CRM/Utils/Geocode/Google.php where a null state_province_id is set to the character string 'null'.  This looks like a valid id, so the system tries to find it and fails.