ucwords('') returns a type of boolean but it should return ''. This script demonstrates the problem:

<?php
$s="a bc";
$s2=ucwords($s);
echo gettype($s2).":".$s2;
$s='';
$s2=ucwords($s);
echo gettype($s2).":".$s2;
?>

To get around it I do this after the ucwords() call:
  if(!$s2)$s2='';