title: "Application windows are expected to have a root view controller at the end of application launch" error only on iPad
body: <p>I am trying to convert my iPhone only application to a Universal application. I switched the devices to Universal and let Xcode do it's thing making a MainWindow-iPad.xib for me, and now when I run the app in the iPhone simulator it works fine, but when I run it in the iPad simulator I get a white screen and the <code>Application windows are expected to have a root view controller at the end of application launch</code> error. I have read some other posts about this same problem but none of them are just limited to one device.</p>
  
  <p>Here is my <code>application:didFinishLaunchWithOptions:</code> method:</p>
  
  <pre><code>- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
  {
  
   /* some dropbox setup stuff */
  
  
  // INIT VIEW AND CORE DATA
  RootViewController *rootViewController = [[RootViewController alloc] initWithNibName:@"RootViewController" bundle:nil];
  
  NSManagedObjectContext *context = [self managedObjectContext];
  if (!context) {
      // Handle the error.
  }
  
  rootViewController.managedObjectContext = context;
  
  UINavigationController *aNavigationController = [[UINavigationController alloc] initWithRootViewController:rootViewController];
  self.navigationController = aNavigationController;
  
  [_window addSubview:[_navigationController view]];
  [_window makeKeyAndVisible];
  
  [rootViewController release];
  [aNavigationController release];
  
  return YES;
  }
  </code></pre>
  
  <p>EDIT: I just have one root view controller that is sized for iPhone called RootViewController. But it should still load in shouldn't it? Or if it shouldn't how do I create one for iPad?</p>