swift UIでcore dataを使用しwkwebviewで表示したページのURLを保存する方法を教えてください

swift UIでwebブラウザを制作しています。ブラウザの閲覧履歴をcore dataを使用して保存したいのですが、wkwebview上で保存しようとしたところ”Foundation._GenericObjCError.nilError”が発生しクラッシュしてしまいます。解決方法を教えて頂けないでしょうか？

ContentView.swift

swift
1import SwiftUI
2import WebKit
3import CoreData
4
5struct ContentView: View {
6    @Environment(\.managedObjectContext) private var viewContext
7
8    @FetchRequest(
9        sortDescriptors: [NSSortDescriptor(keyPath: \Item.timestamp, ascending: true)],
10        animation: .default)
11    private var items: FetchedResults<Item>
12    
13    var body: some View {
14        NavigationView {
15            VStack{
16                ZStack{
17                    VStack{
18                        Text("閲覧数")
19                        
20                        Text(items.count.description)
21                    }
22                    NavigationLink(destination: WbView()) {
23                    Text("web閲覧")
24                            )
25                }
26            }
27                NavigationLink(destination: HistoryView()) {
28                    Text("履歴")
29                }
30            }
31        }
32    }
33}
34struct WbView: View {
35    @Environment(\.managedObjectContext) private var viewContext
36    var body: some View {
37        //WebView()
38        WebView(urlString: "https://www.google.com/")
39            .environment(\.managedObjectContext, viewContext)
40    }
41}

WebView.swift

swift
1import SwiftUI
2import WebKit
3import CoreData
4
5struct WebView: UIViewRepresentable {
6    var webView = WKWebView()
7    var urlString: String
8
9    class Coordinator: NSObject, WKUIDelegate, WKNavigationDelegate {
10        var parent: WebView
11        
12        init(_ parent: WebView) {
13            self.parent = parent
14        }
15        
16        func webView(_ webView: WKWebView, decidePolicyFor navigationAction: WKNavigationAction, decisionHandler: (WKNavigationActionPolicy) -> Void) {
17            if let url = navigationAction.request.url?.absoluteString {
18                if (url.hasPrefix("https://")) {
19                    decisionHandler(WKNavigationActionPolicy.allow)
20                } else {
21                    guard let appStoreLink = URL(string: url) else {
22                        return
23                    }
24                    UIApplication.shared.open(appStoreLink, options: [:], completionHandler: { (succes) in
25                    })
26                    decisionHandler(WKNavigationActionPolicy.cancel)
27                }
28            }
29        }
30        // 表示しているページ情報
31        func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
32            // 表示しているページのURL
33            let urlText = webView.url?.absoluteString ?? ""
34            // 表示しているページのタイトル
35            let titleText = webView.title ?? ""
36            
37            let newItem = Item(context: viewContext)
38            newItem.timestamp = Date()
39            newItem.title = titleText
40            newItem.url = urlText
41            do {
42                try viewContext.save()
43            } catch {
44                // Replace this implementation with code to handle the error appropriately.
45                // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
46                let nsError = error as NSError
47                fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
48            }
49        }
50    }
51    
52    func makeCoordinator() -> Coordinator {
53        Coordinator(self)
54    }
55    
56    func makeUIView(context: Context) -> WKWebView {
57        let webView = WKWebView()
58        return webView
59    }
60    
61    func updateUIView(_ webView: WKWebView, context: Context) {
62        webView.uiDelegate = context.coordinator
63        webView.navigationDelegate = context.coordinator
64        guard let url = URL(string: urlString) else {
65            return
66        }
67        let request = URLRequest(url: url)
68        webView.load(request)
69    }
70}