// in CaseContainer.swift 
public var tabBarHeight: CGFloat {
        guard let homeIndicator = UIApplication.shared.windows.first,
            let tabBarController = vc.tabBarController else {
                return 0
        }
        var tabBarHeight = tabBarController.tabBar.frame.height
        
        if #available(iOS 11.0, *) {
            let homeIndicatorHeight = homeIndicator.safeAreaInsets.bottom
            // MARK: issues: having different Value at the same point when having UINavigationBar or not having UINavigationBar
            // temporary expedient at not.
            // in iPhoneX serise, UITabBarController.TabBar Height is 49 when having only UITabBarController but UITabBarController.TabBar Height is 49 + 34(home Indicator's height) when having both UITabBarController and UINavigationController.
            // the same instance has different value at the same point. I don't know reason. now(2018.10.10)
            // and when having UINavigationController.navigationBar, to be forced safe area constraint in the bottom
            tabBarHeight = tabBarHeight > 50 ? (tabBarHeight - homeIndicatorHeight) : tabBarHeight
            return tabBarHeight + homeIndicatorHeight
        } else {
            return tabBarHeight
        }
    }