         
         if interactivePopGestureRecognizerEnabled,
             let viewController = contentViewController as? UINavigationController
-            where viewController.viewControllers.count > 1 && viewController.interactivePopGestureRecognizer.enabled {
+            where viewController.viewControllers.count > 1 && (viewController.interactivePopGestureRecognizer?.enabled ?? false) {
                 return false
         }
         

    
    private func removeMotionEffects(targetView: UIView) {
        
        if let targetViewMotionEffects = targetView.motionEffects {
            for effect in targetViewMotionEffects {
                targetView.removeMotionEffect(effect as! UIMotionEffect)
            }
        }

        
        if iOS8 {
            if let cntentViewStoryboardID = contentViewStoryboardID {
                contentViewController = storyboard?.instantiateViewControllerWithIdentifier(cntentViewStoryboardID)
            }
            if let lftViewStoryboardID = leftMenuViewStoryboardID {
                leftMenuViewController = storyboard?.instantiateViewControllerWithIdentifier(lftViewStoryboardID)
            }
            if let rghtViewStoryboardID = rightMenuViewStoryboardID {
                rightMenuViewController = storyboard?.instantiateViewControllerWithIdentifier(rghtViewStoryboardID)
            }
        }
        
