Use Of IBOutlet in anotherView Controller?

I have create an app in swift where I'm having floating panel in bottom side, at the click event of floating panel button I want to change the label of the text, floating panel is in .xib file.

I'm showing my whole code with error below,

when btnPress (CardViewController 12 line ) action calles doNothing, at line (ViewController )31 I'm getting error of

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

ViewController

Code Block 
import UIKit
class ViewController: UIViewController {
    enum CardState {
        case expanded
        case collapsed
    }
    var cardViewController: CardViewController!
    var visualEffectView: UIVisualEffectView!
    var cardHeight:CGFloat = 600
    let cardHandleAreaHeight:CGFloat = 65
    var cardVisible = false
    var nextState:CardState {
        return cardVisible ? .collapsed : .expanded
    }
    var runningAnimations = [UIViewPropertyAnimator]()
    var animationProgressWhenInterrupted:CGFloat = 0
    @IBOutlet weak public var txtlbl: UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
        setupCard()
    }
    func doNothing(){
        txtlbl.backgroundColor =  colorLiteral(red: 0.2588235438, green: 0.7568627596, blue: 0.9686274529, alpha: 1)
        print("k")
    }
    func setupCard() {
        cardHeight = self.view.frame.height - 40
        visualEffectView = UIVisualEffectView()
        visualEffectView.frame = self.view.frame
        self.view.addSubview(visualEffectView)
        visualEffectView.isHidden = true
        cardViewController = CardViewController(nibName:"CardViewController", bundle:nil)
        self.addChild(cardViewController)
        self.view.addSubview(cardViewController.view)
        cardViewController.view.frame = CGRect(x: 0, y: 		  self.view.frame.height - cardHandleAreaHeight, width: self.view.bounds.width, height: cardHeight)
        cardViewController.view.clipsToBounds = true
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(ViewController.handleCardTap(recognzier:)))
        let panGestureRecognizer = UIPanGestureRecognizer(target: self, action: #selector(ViewController.handleCardPan(recognizer:)))
cardViewController.handleArea.addGestureRecognizer(tapGestureRecognizer)
cardViewController.handleArea.addGestureRecognizer(panGestureRecognizer)
    }
    @objc
    func handleCardTap(recognzier:UITapGestureRecognizer) {
        switch recognzier.state {
        case .ended:
            animateTransitionIfNeeded(state: nextState, duration: 0.9)
        default:
            break
        }
    }
   
    @objc
    func handleCardPan (recognizer:UIPanGestureRecognizer) {
        cardHeight = self.view.frame.height - 40    
        switch recognizer.state {
        case .began:
            startInteractiveTransition(state: nextState, duration: 0.9)
        case .changed:
            let translation = recognizer.translation(in: self.cardViewController.handleArea)
            var fractionComplete = translation.y / cardHeight
            fractionComplete = cardVisible ? fractionComplete : -fractionComplete
            updateInteractiveTransition(fractionCompleted: fractionComplete)
        case .ended:
            continueInteractiveTransition()
        default:
            break
        }
    }
    func animateTransitionIfNeeded (state:CardState, duration:TimeInterval) {
        cardHeight = self.view.frame.height - 40
        if runningAnimations.isEmpty {
            let frameAnimator = UIViewPropertyAnimator(duration: duration, dampingRatio: 1) {
                switch state {
                case .expanded:
                    self.cardViewController.view.frame.origin.y = self.view.frame.height - self.cardHeight
                    self.visualEffectView.isHidden = false
                case .collapsed:
                    self.cardViewController.view.frame.origin.y = self.view.frame.height - self.cardHandleAreaHeight
                    self.visualEffectView.isHidden = true
                }
            }
               frameAnimator.addCompletion { _ in
                self.cardVisible = !self.cardVisible
                self.runningAnimations.removeAll()
            }
            frameAnimator.startAnimation()
            runningAnimations.append(frameAnimator)
            self.cardViewController.view.layer.cornerRadius = 12
        }
    }
    func startInteractiveTransition(state:CardState, duration:TimeInterval) {
        if runningAnimations.isEmpty {
            animateTransitionIfNeeded(state: state, duration: duration)
        }
        for animator in runningAnimations {
            animator.pauseAnimation()
            animationProgressWhenInterrupted = animator.fractionComplete
        }
    }
    func updateInteractiveTransition(fractionCompleted:CGFloat) {
        for animator in runningAnimations {
            animator.fractionComplete = fractionCompleted + animationProgressWhenInterrupted
        }
    }
    func continueInteractiveTransition (){
        for animator in runningAnimations {
            animator.continueAnimation(withTimingParameters: nil, durationFactor: 0)
        }
    }
}

Second ViewController (.xib)

Code Block 
import UIKit
class CardViewController: UIViewController {
    var dash = ViewController()
    @IBOutlet weak var handleArea: UIView!
    @IBOutlet weak var btn: UIButton!
    @IBOutlet weak var uiViewColor: UIView!
    @IBAction func btnPress(_ sender: Any) {
        print("CardView Function Execute")
        dash.doNothing()
    }
}

I have tried protocols, segue method.

Help me with this,
Thank you in advance.