fix(items): safe cast in _try_return_to_chest, typed chest state param, object_states reset

- Replace unsafe direct cast in HoldableItem._try_return_to_chest() with guarded as-cast
- Type set_chest_state() parameter as Array[String] to match RoomChest._get_spawned_ids()
- Add else-branch in apply_save_data() to reset _object_states when key absent
- Rename test_save_data_has_version_two to test_save_data_has_version_three

scripts/autoload/GameState.gd

@@ -63,7 +63,7 @@ func get_chest_state(chest_id: String) -> Array:
 	return _chest_states.get(chest_id, [])
 
 
-func set_chest_state(chest_id: String, spawned_item_ids: Array) -> void:
+func set_chest_state(chest_id: String, spawned_item_ids: Array[String]) -> void:
 	_chest_states[chest_id] = spawned_item_ids
 	state_changed.emit()
 
@@ -108,6 +108,8 @@ func apply_save_data(data: Dictionary) -> void:
 		_character_held_items = {}
 	if data.has("object_states"):
 		_object_states = data["object_states"]
+	else:
+		_object_states = {}
 	if data.has("current_room"):
 		current_room = data["current_room"]
 	if data.has("music_volume"):