title: Obj-C, NSScanner: nil string argument, suddenly getting this warning, how do I fix it?
body: <p>I'm suddenly getting this warning <code>NSScanner: nil string argument</code> in the debug window.</p>
  
  <p>I say suddenly, but I've no idea from which code has caused it.</p>
  
  <p>How do I resolve this problem ?</p>