Description:
------------
We have in our code the following statement (done via Doctrine):

```
$stmt->bindValue(6, null, 1);
```

coming from an entity property of the type `?int` and for which the corresponding DB column is a nullable integer (PostgreSQL 12.3).

When upgrading from PHP 7.4.13 to 7.4.18 the above statement results in a segfault  once executing the query.

changing the `null` value into an int value or keeping the value `null` and changing the param type `1` to `0` both results in a successful execution on 7.4.18.

The related Doctrie code is https://github.com/doctrine/dbal/blob/2.13.x/lib/Doctrine/DBAL/Statement.php#L101-L121 as you can see it did not change in a log time and even if a failure is expected with an invalid type, I suspect a segfault is not the desired outcome.

Test script:
---------------
We are using the following except locally:

```
$kernel = new Kernel($_SERVER['APP_ENV'], (bool) $_SERVER['APP_DEBUG']);
$kernel->boot();

/** @var PDOStatement $stmt */
$stmt = $kernel->getContainer()
    ->get('doctrine.dbal.default_connection')
    ->prepare('INSERT INTO foo (col1, col2, col3, col4, col5, col6, col7) VALUES (?, ?, ?, ?, ?, ?, ?)');

$stmt->bindValue(1, 16527, 1);
$stmt->bindValue(2, 'ee3b3a2d-f01a-4455-a509-629bf2780ca6', 2);
$stmt->bindValue(3, '2021-05-03T16:09:31Z', 2);
$stmt->bindValue(4, 'certificationGranted', 2);
$stmt->bindValue(5, 'foo', 2);
$stmt->bindValue(6, null, 1);
$stmt->bindValue(7, '3e2456b7-49c2-46de-ad7d-1b3f4c1b5663', 2);

$stmt = $stmt->execute(null);
```


Expected result:
----------------
Not a segfault.