pgsql: Fix Fatal error in _close() method
pgsql: Fix Fatal error in _close() method

On PHP 8, ADORecordSet_postgres64::_close() throws the following error:
Uncaught TypeError: pg_free_result(): Argument #1 ($result) must be of
type resource, bool given in drivers/adodb-postgres64.inc.php:1052.

Adding a check to ensure _QueryID is a ressource of the expected type,
before calling pg_free_result().

Fixes #666

ipso/ADOdb,ipso/ADOdb