关闭期权窗口后，报错内容如下：
Traceback (most recent call last):
File "D:\veighna_studio\lib\site-packages\vnpy_optionmaster\ui\widget.py", line 187, in closeEvent
self.scenario_chart.close()
AttributeError: 'NoneType' object has no attribute 'close'之后再打开期权的窗口，所有按钮都点击不了
