Snapshotting a view that has not been rendered results in an empty snapshot when view presented modally - Swift 3

I have a Table View Controller as a tab. In it, there's a button that takes you to a Facebook profile:

func didTapFacebook() {
        let url = URL(string: "http://www.facebook.com/" + myFacebookId)
        if UIApplication.shared.canOpenURL(url!) {
            UIApplication.shared.open(url!, options: [:], completionHandler: nil)
        }
    }

Works fine every time you press the button. From another tab, there's a button that presents modally a navigation controller with Table View Controller as its root:

func segueToTable(_ sender: UIViewController, tvc: MyTableViewController, completion: @escaping ((_ done: Bool) -> Void)) {
        let nc = MyNavigationController(rootViewController: tvc)
        sender.present(nc, animated: true, completion: {
            completion(true)
        })
    }

…

let storyboard = UIStoryboard(name: "Main", bundle: nil)
let tvc = storyboard.instantiateViewController(withIdentifier: "TVC") as! MyTableViewController
segueToTable(self, tvc: tvc, completion: { done in
      print(“segue complete”)
})

Now once you tap the same button to go to Facebook profile (or Twitter button, basically anything that causes the app to go to background), this warning occurs (there is no keyboard displayed on the screen at this time):

Cannot snapshot view (>) with afterScreenUpdates:NO, because the view is not in a window. Use afterScreenUpdates:YES.

Returning to the app and pressing the button again causes this warning to appear (and every attempt after that):

Snapshotting a view that has not been rendered results in an empty snapshot. Ensure your view has been rendered at least once before snapshotting or snapshot after screen updates.

I realize this is related to snapshotting a view that automatically occurs prior to entering the background. It appears for some reason it doesn't like doing that within a view that was presented modally. I've tried a variety of things based on other posts but cannot get the warnings to go away.

Any help is appreciated.