Invalid null serialization in arrays

[scaytrase]

This code
https://github.com/schmittjoh/serializer/blob/master/src/JMS/Serializer/GenericSerializationVisitor.php#L104-L106

            if (null === $v && ( ! is_string($k) || ! $context->shouldSerializeNull())) {
                continue;
            }

Test

$context = \JMS\Serializer\SerializationContext::create();
$context->setSerializeNull(true);
var_dump($serializer->toArray([1, null, 2], $context));

$context = \JMS\Serializer\SerializationContext::create();
$context->setSerializeNull(true);
var_dump($serializer->serialize([1, null, 2], 'json', $context));

Output

array(2) {
  [0] =>
  int(1)
  [2] =>
  int(2)
}

string(13) "{"0":1,"2":2}"

Dropping null value makes the json_encode think of the data like the named properties. I think correct condition should be

if (null == $v && is_string($k) && !$context->shouldSerializeNull()) {
continue;
}

In this case we drop null only in case they are at hash array, not positional.

[scaytrase]

The given commit actually does not resolve the problem.

It fails a simple test

    public function testNullArraySerialization()
    {
        $context = SerializationContext::create();
        $context->setSerializeNull(true);
        $array = [0, null, 'a'];
        self::assertSame($array, $this->serializer->toArray($array, $context));
    }

How we force an array being normalized as array, not object?