无法理解为什么UINavigationController中存在此工件

Question

Here's the problem

当我在SearchController中单击一个用户时，相对的配置文件会显示出来，但是NavigationController下有一个黑条，当我从左向右滑动回到SearchController时，也会出现相同的问题。谁能帮我？谢谢

这是UserProfile代码

    class UserProfileVC: UICollectionViewController, UICollectionViewDelegateFlowLayout, UserProfileHeaderDelegate {

        override func viewDidLoad() {
            super.viewDidLoad()
            collectionView?.register(FeedCell.self, forCellWithReuseIdentifier: cellId)
            collectionView?.register(UserProfileHeader.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, withReuseIdentifier: headerId)

            view.addSubview(collectionView)
            collectionView.delegate = self
            collectionView.dataSource = self
            setUpNavigationController()
        }

        override func viewWillAppear(_ animated: Bool) {
            super.viewWillAppear(animated)
            navigationController?.navigationBar.prefersLargeTitles = true
        }

        override func viewWillDisappear(_ animated: Bool) {
            super.viewWillDisappear(animated)
            navigationController?.navigationBar.prefersLargeTitles = true
        }

        private func setUpNavigationController() {
            navigationController?.navigationBar.barTintColor = UIColor(white: whitePoint, alpha: 1)
            navigationController?.navigationBar.isTranslucent = false
            navigationController?.navigationBar.tintColor = .black
            navigationController?.navigationBar.setValue(true, forKey: "hidesShadow")
            navigationController?.navigationBar.prefersLargeTitles = true
        }

        // MARK: - UICollectionViewFlowLayout

        func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {
            return CGSize(width: view.frame.width, height: 150)
        }

        // MARK: - UICollectionView

        override func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {
            let header = collectionView.dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: headerId, for: indexPath) as! UserProfileHeader

            header.delegate = self

            header.user = self.user
            navigationItem.title = user?.name

            return header
        }

        override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell{
            let cell = collectionView.dequeueReusableCell(withReuseIdentifier: cellId, for: indexPath) as! FeedCell
            cell.post = posts[indexPath.item]
            return cell
        }
    }