Description:
------------
When NodeList length is int(0), empty($nodes->length) should be true

Reproduce code:
---------------
<?php

$doc = new DOMDocument();
$xpath = new DOMXPath($doc);
$nodes = $xpath->query('*');
var_dump($nodes);
var_dump($nodes->length);
var_dump(empty($nodes->length));


Expected result:
----------------
ket% php tmp.php
object(DOMNodeList)#3 (0) {
}
int(0)
bool(true)
ket% 

Actual result:
--------------
ket% php tmp.php
object(DOMNodeList)#3 (0) {
}
int(0)
bool(false)
ket%