+ [CATransaction synchronization] called in a transaction right at application launch

Question

This is very strange ... A message appears right in application didFinishLaunchingWithOptions. Even with a completely empty method.

Say it like this:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    

    [self.window makeKeyAndVisible];

    return YES;
}

And yes, I know that this does not work, because rootController is not defined for this window. So the application crashes, but I still get this +[CATransaction synchronize] called within transaction.

The application really works and doesn't crash - but it's still weird, damn it, and I would like to get rid of it ...

Any ideas?

[change]

This is where the application stack trace begins ...