widget.py 代码出现问题，无法使用在数据管理中使用已下载的数据。

下载数据后，点击刷新报错
Traceback (most recent call last):
File "c:\vnstudio\lib\site-packages\vnpy\app\data_manager\ui\widget.py", line 191, in refresh_tree
item.setText(5, d["start"].stftime("%Y-%m-%d %H:%M:%S"))
AttributeError: 'str' object has no attribute 'stftime'

点击查看报错
Traceback (most recent call last):
File "c:\vnstudio\lib\site-packages\vnpy\app\data_manager\ui\widget.py", line 296, in show_data
dialog = DateRangeDialog(start, end)
File "c:\vnstudio\lib\site-packages\vnpy\app\data_manager\ui\widget.py", line 415, in init
start.year,
AttributeError: 'str' object has no attribute 'year'

请升级到2.1.4版本，并删除C:\users\administrator.vntrader\database.db文件后重启即可