[Privatization] Fix crash on assign inside Arg on ChangeReadOnlyVariableWithDefaultValueToConstantRector

[samsonasik]

Given the following code:

final class SkipAssignInsideArg
{
    public function run()
    {
        $c = base64_decode(str_replace(['--', '_'], ['+', '/'], $key));

        $ivlen = openssl_cipher_iv_length($cipher = "AES-128-CFB");
        $hmac = substr($c, $ivlen, $sha2len = 32);
        $ciphertext_raw = substr($c, $ivlen + $sha2len);
    }
}

cause crash:

Time: 00:00.882, Memory: 78.50 MB

There was 1 error:

1) Rector\Tests\Privatization\Rector\Class_\ChangeReadOnlyVariableWithDefaultValueToConstantRector\ChangeReadOnlyVariableWithDefaultValueToConstantRectorTest::test with data set #6
LogicException: leaveNode() returned invalid value of type integer

/Users/samsonasik/www/rector-src/vendor/nikic/php-parser/lib/PhpParser/NodeTraverser.php:168
/Users/samsonasik/www/rector-src/vendor/nikic/php-parser/lib/PhpParser/NodeTraverser.php:223

Ref https://getrector.com/demo/d7728f83-a22f-4e08-8e76-e10e4b433c5e
Fixes rectorphp/rector#7805

[samsonasik]

Fixed 🎉 /cc @jbcr

[samsonasik]

All checks have passed 🎉 @TomasVotruba it is ready for review.

[TomasVotruba]

Thank you