How does one declare a TableColumn with a nullable field? I have a Book model with several nullable fields: struct Book: Codable, Equatable, Identifiable { // ... let productURL: String? // ... } This is how I'm trying define the corresponding TableColumn: TableColumn("Product URL", value: \.productURL) { book in Text(String(book.productURL ?? "")) } Though this results in several errors: Referencing initializer 'init(_:value:comparator:content:)' on 'TableColumn' requires that 'Book' inherit from 'NSObject' Referencing initializer 'init(_:value:comparator:content:)' on 'TableColumn' requires that 'Book' inherit from 'NSObject' Referencing initializer 'init(_:value:comparator:content:)' on 'TableColumn' requires the types 'KeyPathComparator' and 'SortDescriptor' be equivalent Referencing initializer 'init(_:value:comparator:content:)' on 'TableColumn' requires the types 'KeyPathComparator' and 'SortDescriptor' be equivalent Other, non-nullable columns work just fine. For example: TableColumn("ID", value: \.id) { book in     Text(String(book.id)) } TableColumn("Slug", value: \.slug) TableColumn("Category", value: \.category) TableColumn("Title", value: \.title) // ...