Hello, i have got an error with doctrine 2.3.4 when i try to run the following code :

 
    $conn->executeQuery(
        'INSERT INTO FOO (foo, bar) values (:foo, :bar)', 
         array('foo' => 1, 'bar' => null)
     );

Error : Value for :bar not found in params array. Params array key should be "bar"

This code worked with doctrine 2.3.3.

I think the error comes from the function 'extractParam' in SQLParserUtils.php (DBAL)

line 215 : if (isset($paramsOrTypes[$paramName]))

The key exists even if the value is null.
So it should be:

  if (array_key_exists($paramName, $paramsOrTypes)) 

I am not enough confident to try a PR.
Thanks in advance!