title: Scrapy: skip item and continue with exectuion
body: <p>I'm doing a RSS spider. I want to continue with the execution of the
  spider ignoring the current node if there isn't a match in the current
  item... So far I've got this: </p>
  
  <pre><code>        if info.startswith('Foo'):
              item['foo'] = info.split(':')[1]
          else:
              return None
  </code></pre>
  
  <p>(info is a string that's sanitized from a xpath before...) </p>
  
  <p>But I'm getting this exception: </p>
  
  <pre><code>    exceptions.TypeError: You cannot return an "NoneType" object from a
  </code></pre>
  
  <p>spider</p>
  
  <p>So how can I ignore this node and continue with the execution?</p>