iOS 崩溃的原因是什么 UICollectionView 收到索引路径不存在的单元格的布局属性

iOS 崩溃的原因是什么？ UICollectionView 收到索引路径不存在的单元格的布局属性

swift
class MyCollectionViewDataSource: NSObject, UICollectionViewDataSource {
    var data = [String]()
    func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return data.count
    }
    func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "MyCell", for: indexPath) as! MyCell
        cell.textLabel.text = data[indexPath.row]
        return cell
    }
}
class ViewController: UIViewController {
    @IBOutlet weak var collectionView: UICollectionView!
    var dataSource = MyCollectionViewDataSource()
    override func viewDidLoad() {
        super.viewDidLoad()
        collectionView.dataSource = dataSource
        dataSource.data = ["Item 1", "Item 2", "Item 3"]
        collectionView.reloadData()
    }
    // ...
    // Some code to delete or insert cells
    // ...
}