Fix error in edit view on NULL oid
Chemistry still uses large objects for its image storage. On PHP 8.1 when going into edit view for a row with an oid column we get
PHP Fatal error: Uncaught TypeError: pg_lo_read_all(): Argument #1 ($lob) must be of type PgSql\Lob, bool given in /var/www/hotwire3/dev/chem/dbdev/chemistry/classes/dbDispOid.php
This change checks the return value of pg_lo_open() isn't FALSE before trying to use it.