title: NSFetchedResultsController crash when using CONTAINS in predicate
body: <p>Entity contains <code>CLPlacemark</code> property. 
  I want to check if <code>city</code> string matches to locality property of placemark.</p>
  
  <p>Crash happens on <code>performFetch</code> when I use <code>CONTAINS</code> in predicate.</p>
  
  <pre><code>predicate = [NSPredicate predicateWithFormat:@"placemark.locality CONTAINS[cd] %@", city];
  [_fetchedResultsController.fetchRequest setPredicate:predicate];
          NSError *error = nil;
          if (![[self fetchedResultsController] performFetch:&amp;error]) {
              NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
              abort();
          }
  </code></pre>