[ios] Applications are expected to have a root view controller at the end of application launch

I came across the same issue but I was using storyboard

Assigning my storyboard InitialViewController to my window's rootViewController.

In

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{
...
UIStoryboard *stb = [UIStoryboard storyboardWithName:@"myStoryboard" bundle:nil];
self.window.rootViewController = [stb instantiateInitialViewController];
return YES;
}

and this solved the issue.