当UISearchBar为空时，UISearchController结果TableViewController不会清除结果

import UIKit

class ViewController: UIViewController, UISearchResultsUpdating {

    var searchController: UISearchController!

    override func viewDidLoad() {
        super.viewDidLoad()

        let resultsTableViewController = UITableViewController(style: .plain)
        resultsTableViewController.tableView.register(UITableViewCell.self, forCellReuseIdentifier: "cell")

        searchController = UISearchController(searchResultsController: resultsTableViewController)
        searchController.searchResultsUpdater = self
        searchController.obscuresBackgroundDuringPresentation = false
        searchController.searchBar.placeholder = "Search items"
        navigationItem.searchController = searchController
        definesPresentationContext = true
    }

    // MARK: - UISearchResultsUpdating

    func updateSearchResults(for searchController: UISearchController) {
        let searchBar = searchController.searchBar
        let tableView = searchController.searchResultsController?.tableView

        if searchBar.text?.isEmpty == true {
            tableView?.reloadData()
        } else {
            // Perform your search here and update the table view
            // For example:
            let searchResults = performSearch(with: searchBar.text ?? "")
            (searchController.searchResultsController as? UITableViewController)?.tableView.reloadData()
        }
    }

    func performSearch(with searchText: String) -> [String] {
        // Implement your search logic here
        return []
    }
}