title: window.open() returns undefined or null on 2nd call
body: <p>I have the follow scenario:</p>
  
  <p>I click a link which:
  opens a popup window called 'popup' which loads a pdf inside of it (in IE6).</p>
  
  <p>without closing the popup, i click the link again, which should reopen the pdf inside the popup, but instead a javascript error in thrown:
  <strong>member not found</strong></p>
  
  <p>the javascript function used to open the popup is:</p>
  
  <pre><code>function openWindow(url, name, props) {
    var windowRef = window.open(url, name, props);
    if (!windowRef.opener) {
      windowRef.opener = self;
    }
    windowRef.focus(); //error at this line, windowRef must be null
    return windowRef;
  }
  </code></pre>
  
  <p>question:
  how do i get around this, without opening a new popup window every time?</p>