Fix crash in arrow key movement

src/nodes/world/Cursor.gd

@@ -101,11 +101,11 @@ func _unhandled_input(event: InputEvent) -> void:
 	# Here, we update the cursor's current tile based on the input direction. See the set_tile()
 	# function below to see what changes that triggers.
 	if event.is_action("ui_right"):
-		self.tile += Vector2.RIGHT
+		self._tile += Vector2.RIGHT
 	elif event.is_action("ui_up"):
-		self.tile += Vector2.UP
+		self._tile += Vector2.UP
 	elif event.is_action("ui_left"):
-		self.tile += Vector2.LEFT
+		self._tile += Vector2.LEFT
 	elif event.is_action("ui_down"):
-		self.tile += Vector2.DOWN
+		self._tile += Vector2.DOWN