Terminar la aplicación debido a la exception no detectada 'NSInternalInconsistencyException', motivo: 'no hay object en el índice 2 en la sección en el índice 0'

Tener una aplicación que use tableview y NSFetchedResultsController. Recibo el error: Terminar la aplicación debido a la exception no NSInternalInconsistencyException ' NSInternalInconsistencyException ', motivo: ' no object at index 2 in section at index 0 '

……… para la línea de object de cosa que da el error. El proyecto es una tabla de la cual la order de visualización es un atributo.

 - (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)sourceIndexPath toIndexPath:(NSIndexPath *)destinationIndexPath; { NSMutableArray *things = [[fetchedResultsController fetchedObjects] mutableCopy]; // Grab the item we're moving. NSManagedObject *thing = [[self fetchedResultsController] objectAtIndexPath:sourceIndexPath]; // Remove the object we're moving from the array. [things removeObject:thing]; // Now re-insert it at the destination. [things insertObject:thing atIndex:[destinationIndexPath row]]; // All of the objects are now in their correct order. Update each // object's displayOrder field by iterating through the array. int i = 0; for (NSManagedObject *mo in things) { [mo setValue:[NSNumber numberWithInt:i++] forKey:@"displayOrder"]; } //[things release], things = nil; [__managedObjectContext save:nil]; } - (NSFetchedResultsController *)fetchedResultsController { if (fetchedResultsController != nil) return fetchedResultsController; fetchRequest = [[NSFetchRequest alloc] init]; entity = [NSEntityDescription entityForName:@"Project" inManagedObjectContext:[self managedObjectContext]]; [fetchRequest setEntity:entity]; NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"displayOrder" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:__managedObjectContext sectionNameKeyPath:nil cacheName:@"ThingsCache"]; aFetchedResultsController.delegate = self; [self setFetchedResultsController:aFetchedResultsController]; return fetchedResultsController; }