title: navigationbar setBackgroundImage not working on iOS15
body: <pre><code>- (void)viewDidLoad {
     [super viewDidLoad];
     [self.navigationController.navigationBar setBackgroundImage:xxx] forBarMetrics:UIBarMetricsDefault];
     [self.navigationController.navigationBar setBarTintColor:[UIColor redColor]];
  }
  </code></pre>
  <p>it works perfect on iOS14.
  but on iOS15, XCode13 beta, it doesn't work anymore.</p>