title: TypeError: Argument 1 of Window.getDefaultComputedStyle does not implement interface Element
body: <p>I have the following code outside my polymer element (in another polymer):</p>
  
  <pre><code>        $(mainThis.shadowRoot.querySelector('#test1')).click(function(e){
              mainThis.$.testelement.openPopup();
          });
  </code></pre>
  
  <p>The line:</p>
  
  <pre><code>mainThis.$.testelement.openPopup();
  </code></pre>
  
  <p>Is causing error:</p>
  
  <pre><code>TypeError: Argument 1 of Window.getDefaultComputedStyle does not implement interface Element.
  </code></pre>
  
  <p>openPopup - is my custom function in polymer "testelement".
  The error appears only in FireFox (version 31) on other browsers (Chrome, Safari, Opera) works perfect. How to fix it ?</p>
  
  <p>Edit (openPopup function):</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
      Polymer('popup-element', {
  
          domReady : function() {
              var mainThis = this;
              $(this.$.popup).on('click','.closebutton', function(e){
                  mainThis.closePopup();
              });
          },
          openPopup : function (){
              $(this.$.popup).show();
              return this;
          },
          closePopup : function (){
              $(this.$.popup).hide();
              return this;
          }
      });
  
  &lt;/script&gt;
  </code></pre>