title: What causes "NSScanner: nil string argument"?
body: <p>I got this message when I save data to core data. </p>
  
  <pre><code>NSScanner: nil string argument
  </code></pre>
  
  <p>I didn't use any NSScanner method. Where did it come from?</p>
  
  <p>This is a bug? What should I do with it?</p>
  
  <p>Thanks help, please.</p>