【Swift】UIBarButtonItem Outlet接続されているのにnilになる

Swiftで、コマ撮りを作るアプリを作っています。UICollectionViewでプロジェクト一覧を表示して、削除ボタンを押したら削除できるようにしたいのですが、何回も接続し直しても、何も変わりません。回答お願いします。

ソースコード:

Swift
1//
2//  ProjectsViewController.swift
3//  ________________
4//
5//  Created by ________ ________ on ______.
6//  Copyright © ____ ________ ________. All rights reserved.
7//
8
9import UIKit
10
11class ProjectsViewController: UICollectionViewController {
12    
13    @IBOutlet weak var removeButton: UIBarButtonItem!
14    @IBOutlet weak var renameButton: UIBarButtonItem!
15    
16    var objects = [ProjectItem]()
17    
18    var editProjects = [String]()
19    
20    override func viewDidLoad() {
21        super.viewDidLoad()
22        
23        let objects = try! FileManager.default.contentsOfDirectory(atPath: NSHomeDirectory() + "/Documents")
24        for i in 0..<objects.count {
25            var images = [String]()
26            do {
27                images = try FileManager.default.contentsOfDirectory(atPath: NSHomeDirectory() + "/Documents")
28            } catch {
29                let alert = UIAlertController(title: """
30                    プロジェクト "(objects[i])" を表示できません。破損している可能性があります。
31                    """, message: nil, preferredStyle: .alert)
32                present(alert, animated: true)
33            }
34            if objects[i] != "新規作成" {
35                if images.count != 0 {
36                    self.objects.append(ProjectItem(image: UIImage(contentsOfFile: NSHomeDirectory() + "/Documents/" + objects[i] + "/" + images[0]), forName: objects[i]))
37                } else {
38                    self.objects.append(ProjectItem(image: nil, forName: objects[i]))
39                }
40            }
41        }
42        self.objects.insert(ProjectItem(image: UIImage(systemName: "plus"), forName: "新規作成"), at: 0)
43        
44        let layout = UICollectionViewFlowLayout()
45        layout.itemSize = CGSize(width: view.frame.width / 4 - 20, height: view.frame.width / 4 - 20)
46        layout.sectionInset = UIEdgeInsets(top: 15, left: 15, bottom: 15, right: 15)
47        collectionView.collectionViewLayout = layout
48        self.collectionView.allowsMultipleSelection = false
49    }
50    
51    /* 省略 */
52    
53    func removeItem(at indexPath: IndexPath) {
54        let alert = UIAlertController(title: """
55            コマ撮り "(objects[indexPath.row].string ?? "")" を削除しますか?
56            """, message: "この操作は取り消せません。", preferredStyle: .alert)
57        alert.addAction(UIAlertAction(title: "削除", style: .destructive, handler: { _ in
58            self.objects.remove(at: indexPath.row)
59            self.collectionView.deleteItems(at: [IndexPath(item: indexPath.row, section: 0)])
60        }))
61        alert.addAction(UIAlertAction(title: "キャンセル", style: .cancel, handler: nil))
62        present(alert, animated: true)
63    }
64    
65    func renameItem(at indexPath: IndexPath, oldName: String?) -> String {
66        return oldName ?? ""
67    }
68    
69    override func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
70        return objects.count
71    }
72    
73    override func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
74        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "Project", for: indexPath) as! CustomCell
75        let label = cell.viewWithTag(1) as! UILabel; label.text = objects[indexPath.row].string ?? ""
76        let imageView = cell.viewWithTag(2) as! UIImageView; imageView.image = objects[indexPath.row].image
77        imageView.tintColor = UIColor.white
78        if objects[indexPath.row].string == "新規作成" {
79            imageView.frame = CGRect(x: Int((view.frame.width / 4.0 - 20.0)) / 4, y: Int((view.frame.width / 4.0 - 20.0)) / 4 - 15, width: Int((view.frame.width / 4.0 - 20.0)) / 2, height: Int((view.frame.width / 4.0 - 20.0)) / 2)
80        }
81        cell.backgroundColor = UIColor.systemGray6
82        return cell
83    }
84    
85    override func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
86        guard let cell: CustomCell = collectionView.cellForItem(at: indexPath) as? CustomCell else { return }
87        if self.collectionView.allowsMultipleSelection {
88            if objects[indexPath.row].string ?? "" != "" {
89                cell.isMarked = true
90                editProjects.append(objects[indexPath.row].string ?? "")
91                // 選択されているセルが1子でなければ無効にする
92                self.renameButton.isEnabled = true
93                if editProjects.count != 1 {
94                    self.renameButton.isEnabled = false
95                }
96            }
97        }
98    }
99    
100    override func collectionView(_ collectionView: UICollectionView, didDeselectItemAt indexPath: IndexPath) {
101        guard let cell: CustomCell = collectionView.cellForItem(at: indexPath) as? CustomCell else { return }
102        if self.collectionView.allowsMultipleSelection {
103            cell.isMarked = false
104            editProjects.remove(at: editProjects.firstIndex(of: objects[indexPath.row].string!)!)
105            // 選択されているセルが1子でなければ無効にする
106            self.renameButton.isEnabled = true
107            if editProjects.count != 1 {
108                self.renameButton.isEnabled = false
109            }
110        }
111    }
112    
113    private func saveImage(image: UIImage, at url: URL) -> Bool {
114        //pngで保存する場合
115        let pngImageData = image.pngData()
116        do {
117            try pngImageData!.write(to: url)
118        } catch {
119            //エラー処理
120            return false
121        }
122        return true
123    }
124    
125    func createDir(atPath dirPath: String) throws {
126        let fileManager = FileManager.default
127        do {
128            try fileManager.createDirectory(atPath: dirPath, withIntermediateDirectories: true, attributes: nil)
129        } catch {
130            // エラーの場合
131            throw NSError(domain: error.localizedDescription, code: NSURLErrorCannotCreateFile, userInfo: nil)
132        }
133    }
134    
135
136    /*
137    // MARK: - Navigation
138
139    // In a storyboard-based application, you will often want to do a little preparation before navigation
140    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
141        // Get the new view controller using segue.destination.
142        // Pass the selected object to the new view controller.
143    }
144    */
145
146}