title: scriptaculous ajax autocomplete empty response
body: <p>I’m working with the ajax-autocompleter which works great.
  My aim is to redirect between an editing function for an existing item, or a creating function for a not-found item.</p>
  
  <p>I insert a specific id to each li, and I can therefore use it for the editing function with an afterUpdateElement option.</p>
  
  <p>But if no results are found, the list is empty, and I can’t find any way to tell the afterUpdateElement script that no results were found.
  Indeed, no afterUpdateElement is called, since there is no selection. So afterUpdateElement is useless…</p>
  
  <p>I was thinking about testing the full value sent by the ajax request.
  But I didn’t find how to grab it…</p>