[TYPO3-mvc] Failing when insert a record

[TSniper]

Fatal error: Call to a member function fetch_assoc() on a non-object in C:\wamp\www\typo3art\typo3\sysext\core\Classes\Database\DatabaseConnection.php on line 1034

My action is :

$query = $this->createQuery();	
		$query->getQuerySettings()->setReturnRawQueryResult(TRUE);
		
		$query->statement("INSERT INTO domain_model_person (pid, showdetails ) VALUES
(136, 0);" );
		return $query->execute();

TYPO3 version : 6.1.5