我有一个基于Firebase数据填充的UICollectionView。我已经创建了填充UICollectionView的自定义单元格：

import UIKit
import Material

class PollCell: CollectionViewCell {

var key: String? {
get {
return self.key
}
}
@IBOutlet weak var imageView: UIImageView!
@IBOutlet weak var pollQuestion: UILabel!

public required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)

    }
}

我试图访问UICollectionView中单击的单元格的pollQuestion变量，并将其传递给另一个ViewController：

     override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "toPoll" {
    let pollViewController = segue.destination as! PollController
        if let cell = sender as? PollCell {
            pollViewController.passLabel.text = cell.pollQuestion.text
        }
    }
}

PollController：

import UIKit

class PollController: UIViewController {

@IBOutlet weak var passLabel: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.
}

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

}

更新：我已经修改了代码，现在收到错误

该应用程序在运行时崩溃，我正在尝试解决：