         addChildViewController(newViewController)
         newViewController.didMoveToParentViewController(self)
         newViewController.view.frame = containerView.bounds
-        containerView.addSubview(newViewController.view)
+        containerView?.addSubview(newViewController.view)
 
         // slide to new view controller
         if let currentViewController = currentStepViewController {

        super.updateView()
        
        navigationItem.rightBarButtonItem?.customView?.hidden = !currentStepViewController!.finalizesFlow
        stepNumberLabel.text = "\(currentStepViewController!.stepNumber)."
        stepIndicationLabel.text = currentStepViewController!.stepIndication
    }
    
    override func configureView() {

    }
    
    private func adjustContentInset(height: CGFloat, duration: NSTimeInterval, options: UIViewAnimationOptions, animated: Bool) {
        bottomInsetConstraint?.constant = height
        view.setNeedsLayout()
        
        if (animated) {
