Description:
------------
Number of properties of serialized object is wrong after setting unknown property and unsetting an existing one. This causes that the object can't be unserialized. See test script.

Test script:
---------------
<?php

class test
{
    public $prop;
}

$test = new test;
$test->unknown = 'test';
unset($test->prop);

print_r(unserialize(serialize($test)));

Expected result:
----------------
test Object
(
    [unknown] => test
)


Actual result:
--------------
PHP Notice:  unserialize(): Unexpected end of serialized data in test.php on line 17
PHP Notice:  unserialize(): Error at offset 39 of 40 bytes in test.php on line 17