Description:
------------
xml_parse_into_struct returns nodes correctly until it encounters an unquoted attribute. The function bombs without error.

Reproduce code:
---------------
<?php
$sample =
  "<?xml version=\"1.0\"?><doc><test attr=unquoted/><next/><again/></doc>";
$parser = xml_parser_create();
$res = xml_parse_into_struct($parser,$sample,$vals,$index);
xml_parser_free($parser);
//var_dump($vals); 
echo sizeof($vals);
?>


Expected result:
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sizeof($vals) is one. Quote the attribute and it should be 5.