Fix DataAccess test on HHVM

HHVM expects constructor arguments to be `null` in `PDOStatement::setFetchMode()` when using `\PDO::FETCH_CLASS` with custom class that does not have a constructor.

```php
PDOException: SQLSTATE[HY000]: General error: user-supplied class does not have a constructor, use NULL for the ctor_params parameter, or simply omit it
```