title: String not loading when using wp_nonce_url and admin_url function
body: <p>I am trying to modify an existing plugin and one of the modifications that I am trying to do is to correct the way buttons are displayed on a certain page. Currently it's like this <a href="http://cl.ly/image/1C1l1H3w0r22" rel="nofollow">http://cl.ly/image/1C1l1H3w0r22</a> (excuse me for pasting screenshot link, I couldn't paste it on here). I am trying to change it to this <a href="http://cl.ly/image/3F2e252y3c41" rel="nofollow">http://cl.ly/image/3F2e252y3c41</a>.</p>
  
  <p>The buttons are loaded, that is working. The action is taking place, that is working. The images are loading, that is working. But for some strange reason the $post->ID is not being loaded.</p>
  
  <p>I am getting wp-admin/?print_pip=true&amp;post&amp;type=print_invoice&amp;_wpnonce=e25508b9df when I should be getting wp-admin/?print_pip=true&amp;post=2712&amp;type=print_invoice&amp;_wpnonce=e25508b9df. 2712 being the order number in this case.</p>
  
  <p>I understand that the problem is this: -</p>
  
  <pre><code>wp_nonce_url(admin_url('?print_pip=true&amp;post='.$post-&gt;ID.'&amp;type=print_invoice'), 'print-pip');
  </code></pre>
  
  <p>Would be great if someone can help me figure out what I am doing wrong.</p>