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

Hi, I have an error in my Xcode project. I am trying to integrate the WebView logic to integrate the following code:

import UIKit
import WebKit


class ViewController: UIViewController {

    @IBOutlet weak var reser: WKWebView!
    @IBOutlet weak var produ: WKWebView!
    @IBOutlet weak var rp: WKWebView!
    @IBOutlet weak var anali: WKWebView!
    @IBOutlet weak var web: WKWebView!
    @IBOutlet weak var du: WKWebView!
    @IBOutlet weak var loginu: WKWebView!
    @IBOutlet weak var logoutu: WKWebView!

    override func viewDidLoad() {
        super.viewDidLoad()

        let reserr = URL(string: "https://google.com")
        let reserrr = URLRequest(url: reserr!)
        reser.load(reserrr)

        let produr = URL(string: "https://google.com")
        let produrr = URLRequest(url: produr!)
        produ.load(produrr)

        let rpr = URL(string: "https://google.com")
        let rprr = URLRequest(url: rpr!)
        rp.load(rprr)

        let analir = URL(string: https://google.com")
        let analirr = URLRequest(url: analir!)
        anali.load(analirr)

        let webr = URL(string: "https://google.com")
        let webrr = URLRequest(url: webr!)
        web.load(webrr)

        let dur = URL(string: "https://google.com")
        let durr = URLRequest(url: dur!)
        du.load(durr)

        let loginur = URL(string: "https://google.com")
        let loginurr = URLRequest(url: loginur!)
        loginu.load(loginurr)

        let logoutur = URL(string: "https://google.com")
        let logouturr = URLRequest(url: logoutur!)
        logoutu.load(logouturr)

    }


}

In the line where it says: reser.load(reserrr) Xcode gives me the following error:

  

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

What is the solution to this problem?

Environment: Xcode 9 but the project was created with Xcode 10 Beta

Swift 4