title: sectionIndexTitlesForTableView line up correctly with sections
body: <p>I've got a table view with many sections, the title for these sections is just A-Z and # just like in the iPhone address book App. I have implemented sectionIndexTitlesForTableView to have the quick move to particular letter and basically just return an array of Letters A - Z and #. </p>
  
  <p>This would work if my list always contains an item for every letter of the alphabet but it won't and this screws up the section index titles because hitting C in the list might go to D if the 3th section is D (ie if there is nothing in section C).</p>
  
  <p>I know I could return the array in sectionIndexTitlesForTableView with only the letters that are sections but this would look a bit odd and not the same functionality as the iPhone Address book app.</p>
  
  <p>How can I rectify this?</p>