How do I change the UIimageview image in the ViewController when the side menu is clicked?

I want to change the background image in the Viewcontroller when one of the side menu items is clicked.

I am using VIP architecture while doing this process.

When the item on the side menu is clicked, the following code block works:

  else if indexPath.row == 1

    {
        switch indexPath.section {
        case 0:
            print("Any ")
            print(indexPath)
        case 1:
            print("Dark Mode ")
          //  self.interactor?.selectThemes(theme: "Dark")
            
            router?.changeTheme(theme: .Dark)
            

        case 2:
            print("Once a day ")
            
        default:
            print("out of range")
        }
    }

then there is something I want to do on the router:

func changeTheme(theme:Themes){
    if Themes.Dark == theme
    {
       var jokegenerate = JokeGenerateController()
        
        jokegenerate.changeBackground(image: UIImage(named: "duck")!)
       
        //print(theme)
        
    }

}

Finally, I want to change the image in the viewController. my code is below:

  func changeBackground(image: UIImage){
    backGroundImage.image = image
    print("hey")
}

But I am getting the following error here: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

What should I do to fix the error?

You should check this link (delegate)

You should create connections between modules.

class Bakery
{
    var delegate:BakeryDelegate?

    func makeCookie()
    {
        var cookie = Cookie()
        cookie.size = 6
        cookie.hasChocolateChips = true

        delegate?.cookieWasBaked(cookie)
    }
}

class CookieShop: BakeryDelegate
{
    func cookieWasBaked(_ cookie: Cookie)
    {
        print("Yay! A new cookie was baked, with size \(cookie.size)")
    }
}
let shop = CookieShop()

let bakery = Bakery()
bakery.delegate = shop

bakery.makeCookie()

Something like that.