Swift При нажатии на item в tabbar происходит краш "UICollectionView must be initialized with a non-nil layout parameter"

Создан UITabBar, при нажатии на item в tabbar происходит краш "UICollectionView must be initialized with a non-nil layout parameter".

UITabBar:

class MainNavigationTabBarController: UITabBarController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        setupNavigationTabBar()
    }
    

    func setupNavigationTabBar() {
        
        
        let promotionsPageViewController = createNavigationController(vc: PromotionsCollectionViewController(), selected: someImage, unselected: someImage, title: "Title")

        viewControllers = [ promotionsPageViewController]
        
        guard let items = tabBar.items else {return}
        for item in items {
            item.imageInsets = UIEdgeInsets(top: 4, left: 0, bottom: -4, right: 0)
        }
   
    }

}

extension UITabBarController {
    
    func createNavigationController(vc: UIViewController, selected: UIImage, unselected: UIImage, title: String) -> UINavigationController {
        let viewControllers = vc
        let navController = UINavigationController(rootViewController: viewControllers)
        navController.tabBarItem.image = unselected
        navController.tabBarItem.selectedImage = selected
        navController.tabBarItem.title = title
        return navController
    }
}
 

его items ведут на UICollectionViewController вроде такого:

class PromotionsCollectionViewController: UICollectionViewController {


override func viewDidLoad() {
    super.viewDidLoad()
    
    let layout = UICollectionViewFlowLayout()
    layout.scrollDirection = .vertical
}

override func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 10
}


override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 1
}
}
extension PromotionsCollectionViewController: UICollectionViewDelegateFlowLayout {

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAt section: Int) -> UIEdgeInsets {
        
        return UIEdgeInsets(top: 32, left: 37.5, bottom: 0, right: 37.5)
    }

    func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        return 19.09
    }
    
    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "promotionCell", for: indexPath) as! PromotionsViewCell
        
        cell.backgroundColor = .white
        cell.layer.borderColor = .grey
        cell.layer.cornerRadius = 14
        
        return cell
    }

}

Пожалуйста подскажите, как исправить ошибку