Doctrine_Query throws exception for custom hydrator that extends stock hydrator

I have a custom hydrator that extends Doctrine_Hydrator_ScalarDriver, for the sole purpose of simplifying the column keys (by passing false as the 3rd parameter on _gatherRowData):

class Doctrine_Hydrator_AssocDriver extends Doctrine_Hydrator_ScalarDriver
{
public function hydrateResultSet($stmt)
{
$cache = array();
$result = array();

while ($data = $stmt->fetch(Doctrine_Core::FETCH_ASSOC))

return $result;
}
}

The processPendingFields method in Doctrine_Query is unnecessarily throwing a Doctrine_Query_Exception at line 465. This can be resolved by skipping hydration methods that extend None, Scalar and SingleScalar.

A diff of the changes is attached.