在摇动时从我的阵列列表中播放随机歌曲时出现异常

Question

我正在开发一个应用程序，它可以播放设备震动中的随机歌曲。以下是我的代码

import UIKit
import AVFoundation

class ViewController: UIViewController {
    var player = AVAudioPlayer()

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }

    override func motionEnded(_ motion: UIEventSubtype, with event: UIEvent?) {
        if event?.subtype == UIEventSubtype.motionShake{
            let soundArray=["firstsong","second","fourth"]
            let randomNumber=Int(arc4random_uniform(UInt32(Int32(soundArray.count))))

            let fileLocation = Bundle.main.path(forResource: soundArray[randomNumber], ofType: "mp3")
            do {
                try player=AVAudioPlayer(contentsOf:URL(fileURLWithPath:fileLocation!))
                player.play()
            }catch{

            }
        }
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

我把我的mp3文件放在音乐文件夹中。当我摇动设备时，我收到以下错误

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

任何帮助将不胜感激