Picker with SwiftData challenges...

Inexperienced "senior" coder here. Learning by imitation, but going relatively well. Keep rebuilding my App and it gets better with each iteration but I then get to the same stumbling block each time... the Product Category and the associated Picker that I am trying to implement.

In my latest iteration, I keep getting the following error in the Xcode Console when running my App in the simulator and going to the associated view:

Picker: the selection "nil" is invalid and does not have an associated tag, this will give undefined results.

I am trying to get a simple Category selection applied to a Product. The Category list is a Model/Array on its own.

@Model
class Category {
    var name: String = ""
    
    var products: [Product]?
    
    init(
        name: String
    ) {
        self.name = name
        self.products = []
    }
}

@Model
class Product {
    var name: String = ""
    
    @Relationship(inverse: \Order.products)
    var orders: [Order]?
    
//    @Relationship(inverse: \Category.products)
    var category: Category?
    
    init(
        name: String,
        category: Category? = nil
    ) {
        self.name = name
        self.orders = []
        self.category = category
    }
}

I cannot select an item in the picker and it is not persisted in the Product record.

struct AddProductView: View {
    @Environment(\.dismiss) private var dismiss
    @Environment(\.modelContext) var context
    @Environment(\.presentationMode) var presentationMode

    @Query(sort: \Category.name) var categories: [Category]
    
    @State private var name: String = ""
    @State private var category: Category?
    
    var body: some View {
        NavigationStack {
            Form {
                TextField("New Product Name", text: $name)
                
                VStack {
                    Section {
                        Picker("Choose a Category?", selection: $category) {
//                            Text("").tag("")
                            ForEach(categories, id:\.self) { category in
                                Text(category.name).tag(category.name)
                            }
                        }
                    }
                }
            }
            .navigationTitle("New Product")
            .navigationBarTitleDisplayMode(.large)
            .toolbar {
                ToolbarItem(placement: .topBarLeading) {
                    Button("Cancel") { dismiss() }
                    }
                // MARK: Need to add data check on name field
                    ToolbarItem(placement: .topBarTrailing) {
                        Button("Save") {
                            let product = Product(name: name)
                            context.insert(product)
                            dismiss()
                    }
                }
            }
        }
    }
}

I must be doing something simple incorrectly, but I cannot see it.

My App is using SwiftData for persistence and is linked to iCloud.

Any thoughts, suggestions, or guidance, would be much appreciated.

Simon