title: Errors thrown from here are not handled
body: <p>I've got this problem trying to parse a JSON on my iOS app:</p>
  
  <p>Relevant code:</p>
  
  <pre><code>let jsonData:NSDictionary = try JSONSerialization.jsonObject(with: urlData! as Data, options: JSONSerialization.ReadingOptions.mutableContainers ) as! NSDictionary
  
  /* XCode error ^^^ Errors thrown from here are not handled */
  </code></pre>
  
  <p>Could anybody help me ?</p>