Improves group features.

- Always show group name when sort mode is by-size.
- Add ineffective group support.

src/App/ViewModels/GameGroupViewModel.swift

@@ -14,6 +14,15 @@ enum GameGroupType: Hashable {
 		}
 	}
 
+	var isValidType: Bool {
+		switch self {
+		case .type, .weakness:
+			return true
+		default:
+			return false
+		}
+	}
+
 	var isType: Bool {
 		if case .type = self {
 			return true

src/App/ViewModels/GameViewModel.swift

@@ -281,48 +281,61 @@ final class GameViewModel: ObservableObject {
 				.sorted()
 		case .weakness:
 			groups = baseMonsters
-				.reduce(into: [:]) { (result: inout [Attack: [GameItemViewModel]], next: GameItemViewModel) in
+				.reduce(into: [:]) { (result: inout [Attack?: [GameItemViewModel]], next: GameItemViewModel) in
 					guard let weaknesses = next.weaknesses else { return }
 
+					var added: Bool = false
 					if weaknesses.contains(where: { $0.1.fire >= .effective }) {
 						if let items = result[.fire] {
 							result[.fire] = items + [next]
 						} else {
 							result[.fire] = [next]
 						}
+						added = true
 					}
 					if weaknesses.contains(where: { $0.1.water >= .effective }) {
 						if let items = result[.water] {
 							result[.water] = items + [next]
 						} else {
 							result[.water] = [next]
 						}
+						added = true
 					}
 					if weaknesses.contains(where: { $0.1.thunder >= .effective }) {
 						if let items = result[.thunder] {
 							result[.thunder] = items + [next]
 						} else {
 							result[.thunder] = [next]
 						}
+						added = true
 					}
 					if weaknesses.contains(where: { $0.1.ice >= .effective }) {
 						if let items = result[.ice] {
 							result[.ice] = items + [next]
 						} else {
 							result[.ice] = [next]
 						}
+						added = true
 					}
 					if weaknesses.contains(where: { $0.1.dragon >= .effective }) {
 						if let items = result[.dragon] {
 							result[.dragon] = items + [next]
 						} else {
 							result[.dragon] = [next]
 						}
+						added = true
+					}
+					if !added {
+						if let items = result[.none] {
+							result[.none] = items + [next]
+						} else {
+							result[.none] = [next]
+						}
 					}
 				}
 				.map { element, baseItems in
 					let items = baseItems.map { monster in
-						IdentifyHolder(monster, prefix: element.prefix)
+						IdentifyHolder(monster, prefix: element?.prefix ?? "n")
 					}
 					return GameGroupViewModel(gameID: gameID, type: .weakness(element: element), items: items)
 				}

src/App/Views/MonsterLists/MonsterList.swift

@@ -12,7 +12,7 @@ struct MonsterList<ItemView: View>: View {
 
 	var body: some View {
 		let items = viewModel.items
-		let isHeaderShow = items.count > 1 || items.first?.type.isType == true
+		let isHeaderShow = items.count > 1 || items.first?.type.isValidType == true
 		List(items) { group in
 			Section {
 				ForEach(group.items) { item in

src/App/Views/MonsterLists/MonsterListColumn.swift

@@ -19,7 +19,7 @@ struct MonsterListColumn: View {
 
 	var body: some View {
 		let items = viewModel.items
-		let isHeaderShow = items.count > 1 || items.first?.type.isType == true
+		let isHeaderShow = items.count > 1 || items.first?.type.isValidType == true
 		List(items, id: \.id, selection: $selectedMonsterID) { group in
 			Section {
 				ForEach(group.items) { item in