fix: changing ball spawning point to avoid context errors

lib/game/pinball_game.dart

@@ -26,7 +26,6 @@ class PinballGame extends Forge2DGame with FlameBloc, KeyboardEvents {
 
   @override
   Future<void> onLoad() async {
-    spawnBall();
     addContactCallback(BallScorePointsCallback());
 
     await add(BottomWall(this));
@@ -123,4 +122,10 @@ class PinballGame extends Forge2DGame with FlameBloc, KeyboardEvents {
 
     return KeyEventResult.handled;
   }
+
+  @override
+  void onAttach() {
+    super.onAttach();
+    spawnBall();
+  }
 }