App crashes when setting variable to nil

Code Block 
struct DestViewStateBinding: View {
    @Binding var theStateBinding: Int
    @Binding var someOpt: Int?
    var body: some View {
        if theStateBinding < 50 { theStateBinding += 10 ; someOpt = nil }
        return Text("Hello, Destination! \(theStateBinding)")
    }
}
struct ContentView: View {
    var contentNoState : Int = 1
    @State var contentState : Int = 1
    @State var contentState2 : Int? = 1
    var body: some View {
        NavigationView {
            VStack {
                NavigationLink(destination: DestViewStateBinding(theStateBinding: $contentState, someOpt: $contentState2)) { 
                    Text("Press on me with Binding")
                }.buttonStyle(PlainButtonStyle())
            }
        }
    }
}

Code Block Swift
switch background {
	case .color:
		ColorPicker("Change color", selection: Binding($color)!) // only works when color is not nil
	...
}

Code Block Swift
if color != nil {
	ColorPicker("Change color", selection: Binding($color)!)
} else {
	ColorPicker("Change color", selection: Binding<Color> {
		Color(.systemBackground)
	} set: {
		color = $0
	})
}

Code Block Swift
struct TestView: View {
	private enum BackgroundType: String, CaseIterable, Identifiable {
		var id: String { self.rawValue }
		case color
		case image
	}
	@State private var backgroundType: BackgroundType = .color
	@Binding var color: Color?
	@Binding var image: UIImage?
	var body: some View {
		NavigationView {
			Form {
				Picker("Background", selection: $backgroundType) {
					ForEach(BackgroundType.allCases) {
						Text($0.rawValue.capitalized).tag($0)
					}
				}
				.pickerStyle(SegmentedPickerStyle())				
				switch backgroundType {
					case .color:
						if color != nil {
							ColorPicker("Change color", selection: Binding($color)!) // error
						} else {
							ColorPicker("Change color", selection: Binding<Color> {
								Color(.systemBackground)
							} set: {
								color = $0
							})
						}
					case .image:
						Image(uiImage: image!)
				}
			}
		}
		.onAppear {
			if image == nil {
				backgroundType = .color
			} else {
				backgroundType = .image
			}
		}
		.toolbar {
			Button("Save") {
				switch backgroundType {
					case .color:
						image = nil
					case .image:
						color = nil // error
				}
			}
		}
	}
}

Code Block 
import SwiftUI
@main
struct Project_BindingApp: App {
    var body: some Scene {
        WindowGroup {
            TestView(color: UIColor.green, image: UIImage(systemName: "checkmark.circle"))
        }
    }
}

Code Block Swift
extension UserDefaults {
	func color(forKey defaultName: String) -> Color? {
		if let data = data(forKey: defaultName) {
			if let color = try? NSKeyedUnarchiver.unarchivedObject(ofClass: UIColor.self, from: data) {
				return Color(color)
			}
		}
		return nil
	}
}
extension URL {
	func loadImage(_ image: inout UIImage?) {
		if let data = try? Data(contentsOf: self), let loaded = UIImage(data: data) {
			image = loaded
		} else {
			image = nil
		}
	}
}

Code Block Swift
private func load() {
	if let color = UserDefaults.standard.color(forKey: "backgroundColor") {
		backgroundColor = color
	} else {
		imageURL.loadImage(&backgroundImage)
	}
}

Code Block Swift
struct ContentView: View {
	@State private var backgroundColor: Color?
	@State private var backgroundImage: UIImage?
	private func load() { ... }
	var body: some View {
		...
		.sheet(...) {
			TestView(color: $backgroundColor, image: $backgroundImage)
		}
		.onAppear(perform: load)
	}
}

Code Block Swift
import SwiftUI
extension URL {
	func loadImage(_ image: inout UIImage?) {
		if let data = try? Data(contentsOf: self), let loaded = UIImage(data: data) {
			image = loaded
		} else {
			image = nil
		}
	}
	func saveImage(_ image: UIImage?) {
		if let image = image {
			if let data = image.jpegData(compressionQuality: 1.0) {
				try? data.write(to: self)
			}
		} else {
			try? FileManager.default.removeItem(at: self)
		}
	}
}
extension UserDefaults {
	func color(forKey defaultName: String) -> Color? {
		if let data = data(forKey: defaultName) {
			if let color = try? NSKeyedUnarchiver.unarchivedObject(ofClass: UIColor.self, from: data) {
				return Color(color)
			}
		}
		return nil
	}
	func set(_ value: Color?, forKey defaultName: String) {
		if let color = value {
			if let data = try? NSKeyedArchiver.archivedData(withRootObject: UIColor(color), requiringSecureCoding: false) {
				set(data, forKey: defaultName)
			}
		} else {
			removeObject(forKey: defaultName)
		}
	}
}
struct ContentView: View {
	@State private var showingTest = false
	@State private var backgroundImage: UIImage?
	@State private var backgroundColor: Color?
	private var imageURL: URL {
		let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
		return paths[0].appendingPathComponent("backgroundImage")
	}
	private func load() {
		if let color = UserDefaults.standard.color(forKey: "backgroundColor") {
			backgroundColor = color
		} else {
			imageURL.loadImage(&backgroundImage)
		}
	}
    var body: some View {
		ZStack {
			GeometryReader { geometry in
				if let image = backgroundImage {
					Image(uiImage: image)
						.resizable()
						.scaledToFill()
						.frame(width: geometry.size.width, height: geometry.size.height)
				} else if let color = backgroundColor {
					color
				} else {
					Color(.systemBackground)
				}
			}
			.ignoresSafeArea()
			Button("Test") {
				showingTest = true
			}
		}
		.onAppear(perform: load)
		.sheet(isPresented: $showingTest) {
			TestView(image: $backgroundImage, color: $backgroundColor)
		}
    }
}
struct TestView: View {
	private enum BackgroundType: String, CaseIterable, Identifiable {
		var id: String { self.rawValue }
		case color
		case image
	}
	@Environment(\.presentationMode) private var presentationMode
	@State private var backgroundType: BackgroundType = .color
	@State private var showingImagePicker = false
	@Binding var image: UIImage?
	@Binding var color: Color?
	private var imageURL: URL {
		let paths = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)
		return paths[0].appendingPathComponent("backgroundImage")
	}
	var body: some View {
		NavigationView {
			Form {
				Section(header: HStack {
					Text("BACKGROUND")
					Spacer()
					HStack {
						Picker("Types of background", selection: $backgroundType) {
							ForEach(BackgroundType.allCases) {
								Text($0.rawValue.capitalized).tag($0)
							}
						}
						.pickerStyle(SegmentedPickerStyle())
						.frame(width: 120)
					}
				}) {
					switch backgroundType {
						case .color:
							if color != nil {
								ColorPicker("Change color", selection: Binding($color)!)
									.foregroundColor(.accentColor)
							} else {
								ColorPicker("Change color", selection: Binding<Color> {
									Color(.systemBackground)
								} set: {
									color = $0
								})
							}
						case .image:
							HStack {
								Button("Change image") {
									showingImagePicker = true
								}
								.sheet(isPresented: $showingImagePicker) {
									PhotoPicker(image: $image)
										.ignoresSafeArea()
								}
								Spacer()
								Image(uiImage: image ?? UIImage(systemName: "questionmark.diamond")!)
									.resizable()
									.scaledToFill()
									.frame(width: 40, height: 40)
									.clipShape(RoundedRectangle(cornerRadius: 10))
							}
					}
				}
			}
			.toolbar {
				ToolbarItem(placement: .confirmationAction) {
					Button("Save") {
						presentationMode.wrappedValue.dismiss()
						
						switch backgroundType {
							case .color:
								image = nil
							case .image:
								color = nil
						}
						
						DispatchQueue.main.async {
							UserDefaults.standard.set(color, forKey: "backgroundColor")
							imageURL.saveImage(image)
						}
					}
				}
			}
		}
		.onAppear {
			if image == nil {
				backgroundType = .color
			} else {
				backgroundType = .image
			}
		}
	}
}
struct PhotoPicker: UIViewControllerRepresentable {
	class Coordinator: PHPickerViewControllerDelegate {
		let parent: PhotoPicker
		init(_ parent: PhotoPicker) {
			self.parent = parent
		}
		func picker(_ picker: PHPickerViewController, didFinishPicking results: [PHPickerResult]) {
			parent.presentationMode.wrappedValue.dismiss()
			if let itemProvider = results.first?.itemProvider, itemProvider.canLoadObject(ofClass: UIImage.self) {
				itemProvider.loadObject(ofClass: UIImage.self) { [weak self] image, error in
					DispatchQueue.main.async {
						guard let self = self, let image = image as? UIImage else { return }
						self.parent.image = image
					}
				}
			}
		}
	}
	@Environment(\.presentationMode) var presentationMode
	@Binding var image: UIImage?
	func makeUIViewController(context: Context) -> some UIViewController {
		var configuration = PHPickerConfiguration(photoLibrary: .shared())
		configuration.filter = .images
		let picker = PHPickerViewController(configuration: configuration)
		picker.delegate = context.coordinator
		return picker
	}
	func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {}
	func makeCoordinator() -> Coordinator {
		Coordinator(self)
	}
}

Here it is in one bit.

The error occurs when the segmented picker it set to Image and the sheet is dismissed.

1. Open the sheet

2. Choose a color

3. Change the segmented picker to image

4. (optional) Choose an image

5. Dismiss the sheet