无法移至其他UIViewControllers

Question

在尝试观看视频然后转到另一个视图控制器时，在代码行Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value while中得到了videoView.layer.addSublayer(playerLayer) 如果有人知道如何解决此问题，我将不胜感激。谢谢。

顺便说一句，这是上下文的完整功能：

@IBOutlet weak var videoView: UIView!
var player: AVPlayer!
var playerLayer: AVPlayerLayer!
var isVideoPlaying = false

override func viewDidLoad() {
    super.viewDidLoad()
    let url = URL(string: "https://content.jwplatform.com/manifests/vM7nH0Kl.m3u8")!
    player = AVPlayer(url: url)

    playerLayer = AVPlayerLayer(player: player)
    playerLayer.videoGravity = .resize

    videoView.layer.addSublayer(playerLayer)
}