iOS 13顶部UIViewController为零

Question

此代码在iOS 12上运行良好- 问题出在iOS 13+ 我知道这与iOS 13场景有关。

extension UIViewController {

    static var top: UIViewController? {
        get {
            return topViewController()
        }
    }

    static var root: UIViewController? {
        get {
            return UIApplication.shared.windows[0].rootViewController
        }
    }

    static func topViewController(from viewController: UIViewController? = UIViewController.root) -> UIViewController? {
        if let tabBarViewController = viewController as? UITabBarController {
            return topViewController(from: tabBarViewController.selectedViewController)
        } else if let navigationController = viewController as? UINavigationController {
            return topViewController(from: navigationController.visibleViewController)
        } else if let presentedViewController = viewController?.presentedViewController {
            return topViewController(from: presentedViewController)
        } else {
            return viewController
        }
    }

}

当我使用iOS 12获得UIViewController.top时，一切正常，但在iOS 13中为零。

任何想法如何解决？