Reworked ugly code

lib/models/game.dart

@@ -1,10 +1,12 @@
+import 'reward.dart';
+
 class Game {
   final int id;
   final String name;
-  final List<Map<String, dynamic>> rewards;
+  final List<Reward> rewards;
 
   Game.fromMap(Map<String, dynamic> map, Iterable<Map<String, dynamic>> rewards)
       : id = map['id'],
         name = map['name'],
-        rewards = rewards.toList();
+        rewards = rewards.map((e) => Reward.fromMap(e)).toList();
 }