New Game Center Sign In Screen: How to know when it is presented, covering my app?

Recently (I'm not sure exactly when), the "Sign in to Game Center" banner started appearing at the top of my app when the app sets the GC authentication handler and there is no Game Center player currently signed in on the device:

So far so good. But if the banner is tapped, a full "Sign In to Game Center" modal view automatically appears and covers the app without notification:

This is not the sign-in view controller that the GC authentication handler normally passes when a player is not signed in, which previously gave my app control over when to present it. My app is unaware that it is covered by this new sign-in screen.

Is there any way for my app to know when the user taps the "Sign In" banner and causes this new automatic sign-in screen to appear? I need to pause my game while it is covered up.

In general, is there a way for my view controller to be notified when it has been covered by a modal view controller that's outside my app's control?