Firebaseに詳しい方

Firebaseにて、アカウントを作りたいのですが、以下のようなエラーが出てきました。

2020-03-09 15:45:20.802697+0900 TwitterClone[2255:56914] - <AppMeasurement>[I-ACS036002] Analytics screen reporting is enabled. Call +[FIRAnalytics setScreenName:setScreenClass:] to set the screen name or override the default screen class name. To disable screen reporting, set the flag FirebaseScreenReportingEnabled to NO (boolean) in the Info.plist
2020-03-09 15:45:21.065080+0900 TwitterClone[2255:56713] [Storyboard] Unknown class _TtC12TwitterClone14ViewController in Interface Builder file.
2020-03-09 15:45:21.183130+0900 TwitterClone[2255:56914] 6.15.0 - [Firebase/Analytics][I-ACS023007] Analytics v.60201000 started
2020-03-09 15:45:21.184481+0900 TwitterClone[2255:56914] 6.15.0 - [Firebase/Analytics][I-ACS023008] To enable debug logging set the following application argument: -FIRAnalyticsDebugEnabled (see http://goo.gl/RfcP7r)
2020-03-09 15:45:22.057951+0900 TwitterClone[2255:56713] Unbalanced calls to begin/end appearance transitions for <TwitterClone.MainTabController: 0x7fb129831a00>.
2020-03-09 15:45:22.104810+0900 TwitterClone[2255:56916] 6.15.0 - [Firebase/Analytics][I-ACS023012] Analytics collection enabled
2020-03-09 15:45:49.308906+0900 TwitterClone[2255:56908] [AutoFill] Cannot show Automatic Strong Passwords for app bundleID: com.gmail.wara56530.TwitterClone due to error: iCloud Keychain is disabled

おそらく、原因はUnbalanced~ のところで調べたらアカウント作成のコントローラーとメインタブの遷移のしかたが悪いらしいです。
それとauthenticateUserAndConfigureUI()のところのDispatchQueの構文の意味がよく分からないです。DispatchQueを書いた後に、いきなりアカウントを作れなくなってしまい、この後どうしたら良いか分からないので、どなたかご教授お願いします。

//
//  MainTabController.swift
//  TwitterClone
//
//  Created by Newton on 2020/02/28.
//  Copyright © 2020 Newton. All rights reserved.
//

import UIKit
import Firebase

enum ActionButtonConfiguration {
    case tweet
    case message
}

class MainTabController: UITabBarController {

    // MARK: - Properties
    
    private var buttonConfig: ActionButtonConfiguration = .tweet
    
    var user: User? {
        didSet {
            guard let nav = viewControllers?[0] as? UINavigationController else { return }
        }
    }
    
    let actionButton: UIButton = {
        let button = UIButton(type: .system)
        button.tintColor = .white
        button.backgroundColor = .twitterBlue
        button.setImage(UIImage(named: "baseline_playlist_add_white_36pt_1x"), for: .normal)
        button.addTarget(self, action: #selector(actionButtonTapped), for: .touchUpInside)
        return button
    }()
    
    // MARK: - Lifecycle
    override func viewDidLoad() {
        super.viewDidLoad()

      //  logUserOut()
        view.backgroundColor = .twitterBlue
        authenticateUserAndConfigureUI()
        
    }
    
    // MARK: - API
    
    func fetchUser() {
        guard let uid = Auth.auth().currentUser?.uid else { return }
//        UserService.shared.fetchUser(uid: uid) { user in
//            self.user = user
//        }
    }
    
    func authenticateUserAndConfigureUI() {
        
        // 原因？
        if Auth.auth().currentUser == nil {
            DispatchQueue.main.async {
                let nav = UINavigationController(rootViewController: LoginController())
                nav.modalPresentationStyle = .fullScreen
                self.present(nav, animated: true, completion: nil)
            }
        } else {
            configureViewController()
            configureUI()
            fetchUser()
        }
    }
    
    func logUserOut() {
        do {
            try Auth.auth().signOut()
        } catch let error {
            print("User is logged in...")
        }
    }
    
    // MARK: - Selector
    @objc func actionButtonTapped() {
        print(123)
    }
    
    // MARK: - Helpers
    
    func configureUI() {
        
        view.addSubview(actionButton)
        actionButton.anchor(bottom: view.safeAreaLayoutGuide.bottomAnchor, right: view.rightAnchor,
                            paddingBottom: 64, paddingRight: 16, width: 56, height: 56)
        actionButton.layer.cornerRadius = 56 / 2
        
    }
    
    func configureViewController() {
        
        let feed = FeedContoroller()
        let nav1 = templateNavigationController(image: UIImage(named: "home_unselected"), rootViewController: feed)
        
        let explore = ExploreContoroller()
        let nav2 = templateNavigationController(image: UIImage(named: "search_unselected"), rootViewController: explore)
        
        let notification = NotificationContoroller()
        let nav3 = templateNavigationController(image: UIImage(named: "like_unselected"), rootViewController: notification)
        
        let conversation = ConversationContoroller()
        let nav4 = templateNavigationController(image: UIImage(named: "ic_mail_outline_white_2x"), rootViewController: conversation)
        
        viewControllers = [nav1, nav2, nav3, nav4]
        
    }
    
    func templateNavigationController(image: UIImage?, rootViewController: UIViewController) -> UINavigationController {
        
        let nav = UINavigationController(rootViewController: rootViewController)
        nav.tabBarItem.image = image
        nav.navigationBar.barTintColor = .white
        return nav
        
    }
    
}

extension MainTabController: UITabBarControllerDelegate {
    func tabBarController(_ tabBarController: UITabBarController, didSelect viewController: UIViewController) {
        let index = viewControllers?.firstIndex(of: viewController)
        let image = index == 3 ? #imageLiteral(resourceName: "mail") : #imageLiteral(resourceName: "new_tweet")
        actionButton.setImage(image, for: .normal)
        buttonConfig = index == 3 ? .message : .tweet
    }
}