终止与NSException类型的未捕获的异常与迅速

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我设置一个userdefualt整数，当我继续到页面的应用程序崩溃。它显示了appDelegate，它显示“线程1：信号SIGBART”，并在调试器中显示“libC++ abi.dylib：终止于类型为NSException的未捕获的异常（lldb）”终止与NSException类型的未捕获的异常与迅速

她是我的代码，请帮我看看这个错误：

class home: UIViewController { 
@IBOutlet weak var fiveth1: UILabel! 
@IBOutlet weak var iron1: UILabel! 
@IBOutlet weak var gold1: UILabel! 
@IBOutlet weak var ships1: UILabel! 
@IBOutlet weak var empires1: UIWebView! 

@IBOutlet weak var webViewG: UIWebView! 
override func viewDidLoad() { 
    super.viewDidLoad() 

    let htmlPath1 = Bundle.main.path(forResource: "WebViewContent2", ofType: "html") 
    let htmlURL1 = URL(fileURLWithPath: htmlPath1!) 
    let html1 = try? Data(contentsOf: htmlURL1) 

    self.webViewG.load(html1!, mimeType: "text/html", textEncodingName: "UTF-8", baseURL: htmlURL1.deletingLastPathComponent()) 


    if (Fiveth.value(forKey: "Fiveth") != nil){ 
     fiveth = Fiveth.value(forKey: "Fiveth") as! NSInteger! 
     fiveth1.text = NSString(format: "Fiveth: %i", fiveth) as String 
    } 

    fiveth1.text = "\(Fiveth)" 
}