The dbase config parameter is not passed to the connection routine in the virtual.class.php file. The easy workaround to this is to specify the database as part of the DSN string in config.ini, for example:
dsn = "pgsql://username:password@localhost/database"
The above workaround fixes the issue but you still have to set the dbase config parameter or the driver will complain and error out that it is not set.
A proper fix will either involve passing the dbase config parameter to the connection routine properly or just scrap the dbase config parameter altogether and instruct people to specify the database in the DSN as per above.