title: JS Error in WordPress WooCommerce: Uncaught TypeError: Cannot set property 'onchange' of null
body: <p>We are using WooCommerce with Wordpress 3.8.3, we've suddenly lost our checkout buttons and add to cart buttons, and see this error in dev tools:</p>
  
  <pre><code>Uncaught TypeError: Cannot set property 'onchange' of null 
  </code></pre>
  
  <p>It also gives the line of the index where the error occurs, but looking at index.php in dev tools is just blank. Any help would be appreciated.</p>
  
  <p><em>Edit</em> I was able to find the index content:</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
   var urlmenu = document.getElementById( 'menu1' );
   urlmenu.onchange = function() 
   {
      window.open(this.options[ this.selectedIndex ].value,'_self');
   };
  &lt;/script&gt;
  </code></pre>