title: Woocommerce and AJAX add to cart broken
body: <p>I have got problem with Woocommerce.
  When I click multiple times "add_to_cart_button" on archive-page.php AJAX stops working and redirects to product page.</p>
  
  <p>First I checked the server response and its just fine. 200 OK :)</p>
  
  <p>Then i looked into scripts. I found add-to-cart.js:</p>
  
  <pre><code>if ( response.error &amp;&amp; response.product_url ) {
     window.location = response.product_url;
     return;
  }
  </code></pre>
  
  <p>Great, I added simple alert:</p>
  
  <pre><code>if ( response.error &amp;&amp; response.product_url ) {
     alert(response.error);
     window.location = response.product_url;
     return;
  }
  </code></pre>
  
  <p>Ok, "response.error" is equal to <em>true</em> when script is moving into this if... But why this if statement is being true? How can I read error status? $.fail doesn't work.</p>
  
  <p>What is going on? Please help :/</p>