[Xcode] 写真のクロップ

以下の参考サイトを参考にSwift4に変えながらコードを書いていたところ、

Swift
1 imageCropVC.delegate = self as? RSKImageCropViewControllerDelegate
2            imageCropVC.dataSource = self as! RSKImageCropViewControllerDataSource

の部分でThread 1: signal SIGABRTとエラーが出てしまいます。実行するまでは何もエラーが出ないのですが写真を選択するとアプリが落ちてエラーが出ます。
どうしたらよいでしょうか？

参考サイト

コード全体

Swift
1import UIKit
2import RSKImageCropper
3
4class SettingViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate  {
5
6    var selectedimage: UIImage?
7    let userDefaults = UserDefaults.standard
8    override func viewDidLoad() {
9        super.viewDidLoad()
10        // Do any additional setup after loading the view.
11    }
12
13    override func didReceiveMemoryWarning() {
14        super.didReceiveMemoryWarning()
15        // Dispose of any resources that can be recreated.
16    }
17    
18    @IBAction func picPicture(_ sender: Any) {
19        if UIImagePickerController.isSourceTypeAvailable(.photoLibrary) {
20            let pickerView = UIImagePickerController()
21            pickerView.sourceType = .photoLibrary
22            pickerView.delegate = self
23            self.present(pickerView, animated: true)
24        }
25    }
26    
27    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
28        selectedimage = info[UIImagePickerControllerOriginalImage] as! UIImage
29        self.dismiss(animated: true)
30        if let image = selectedimage {
31            var imageCropVC: RSKImageCropViewController = RSKImageCropViewController(image: image, cropMode: RSKImageCropMode.custom)
32            imageCropVC.delegate = self as? RSKImageCropViewControllerDelegate
33            imageCropVC.dataSource = self as! RSKImageCropViewControllerDataSource
34            self.navigationController?.pushViewController(imageCropVC, animated: true)
35        }
36    }
37    
38    // キャンセルがおされたらトリミング画面を閉じます
39    func imageCropViewControllerDidCancelCrop(controller: RSKImageCropViewController!) {
40        self.navigationController?.popViewController(animated: true)
41    }
42    
43    func imageCropViewController(controller: RSKImageCropViewController!, willCropImage originalImage: UIImage!) {
44    }
45    
46    // トリミング済みの画像がかえされます
47    func imageCropViewController(controller: RSKImageCropViewController!, didCropImage croppedImage: UIImage!, usingCropRect cropRect: CGRect) {
48        let imageData = UIImageJPEGRepresentation(croppedImage, 1);
49        userDefaults.set(imageData, forKey: "image")
50        userDefaults.synchronize()
51    }
52    
53    func imageCropViewControllerCustomMaskRect(controller: RSKImageCropViewController!) -> CGRect {
54        
55        var maskSize: CGSize
56        var width, height: CGFloat!
57        
58        width = self.view.frame.width
59        
60        // 縦横比 = 1 : 2でトリミングしたい場合
61        height = self.view.frame.width / 2
62        
63        maskSize = CGSize(width: self.view.frame.width, height: height)
64        
65        var viewWidth: CGFloat = controller.view.frame.width
66        var viewHeight: CGFloat = controller.view.frame.height
67        
68        var maskRect: CGRect = CGRect(x: (viewWidth - maskSize.width) * 0.5, y: (viewHeight - maskSize.height) * 0.5, width: maskSize.width, height: maskSize.height)
69        
70        return maskRect
71    }
72    
73    // トリミングしたい領域を描画（今回は四角な領域です・・・）
74    func imageCropViewControllerCustomMaskPath(controller: RSKImageCropViewController!) -> UIBezierPath! {
75        var rect: CGRect = controller.maskRect
76        var point1: CGPoint = CGPoint(x: rect.minX, y:rect.maxY)
77        var point2: CGPoint = CGPoint(x:     rect.maxX, y:rect.maxY)
78        var point3: CGPoint = CGPoint(x:     rect.maxX, y:rect.minY)
79        var point4: CGPoint = CGPoint(x:     rect.minX, y:rect.minY)
80        var square: UIBezierPath = UIBezierPath()
81        square.move(to: point1)
82        square.addLine(to: point2)
83        square.addLine(to: point3)
84        square.addLine(to: point4)
85        square.close()
86        
87        return square
88    }
89    
90    func imageCropViewControllerCustomMovementRect(controller: RSKImageCropViewController!) -> CGRect {
91        return controller.maskRect
92    }
93
94}
95