在Swift中集成Sinch第三方库时出错？

Question

我想在我的应用程序中构建视频通话功能，因此我决定选择Sinch框架。但是当我按通话时，似乎localView无法跟踪。请帮助我解决此问题。非常感谢。这是我的代码获取错误：

func videoController() -> SINVideoController {
   let appDel = UIApplication.shared.delegate as! AppDelegate
   return (appDel.client?.videoController())!
}

我在return行中收到此错误：

Thread 1: EXC_BREAKPOINT (code=1, subcode=0x102bcc740)

这是我的代码：

override func viewDidLoad() {
    super.viewDidLoad()

    sinCall?.delegate = self

    playSound()

    if sinCall?.direction == SINCallDirection.incoming { 
        lbReceiverName.text = "Đang gọi"
        _ = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(updateLabelForReceiver), userInfo: nil, repeats: true)
        if let id = senderName {
            databaseRefenrence.child("Users").child("\(id)").observeSingleEvent(of: .value, with: { (snapshot) in
                if let dict = snapshot.value as? [String : Any] {
                    self.lbDangGoi.text = dict["Name"] as? String
                }
            })
        }
        localView.isHidden = false
        btAccept.isHidden = false
        btDecline.isHidden = false
        btEnd.isHidden = true
    } else {
        _ = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(updateLabelForSender), userInfo: nil, repeats: true)
        if let name = receiverName {
            lbReceiverName.text = name
        }
        localView.isHidden = false
        btAccept.isHidden = true
        btDecline.isHidden = true
        btEnd.isHidden = false
    }

    if sinCall?.details.isVideoOffered == true {
        localView.addSubview((videoController().localView())!)
    }
}

func callDidAddVideoTrack(_ call: SINCall!) {
    remoteView.addSubview((videoController().remoteView())!)
}