message: Avoided viewWithTag if already at scene
  Can't think of a case where there's a stack in a scene. Even if there is it's not so bad if the scene controls the status bar?!
diff: - (UIViewController *)navigation_childViewControllerForStatusBarStyle
  {
  + if ([self isKindOfClass:[NVSceneController class]])
  + return nil;
  NVNavigationStackView *stack = (NVNavigationStackView *) [self.view viewWithTag:NAVIGATION_STACK];
  return [stack.navigationController presentedViewController] ?: [stack.navigationController topViewController];
  }
  