回测下载数据出现错误：
File "e:\VNConda\lib\site-packages\vnpy\trader\database\database_sql.py", line 144, in save_all
DbBarData.insert_many(c).on_conflict_replace().execute()
File "e:\VNConda\lib\site-packages\peewee.py", line 1737, in inner
return method(self, database, *args, **kwargs)
File "e:\VNConda\lib\site-packages\peewee.py", line 1808, in execute
return self._execute(database)
File "e:\VNConda\lib\site-packages\peewee.py", line 2512, in _execute
return super(Insert, self)._execute(database)
File "e:\VNConda\lib\site-packages\peewee.py", line 2275, in _execute
cursor = database.execute(self)
File "e:\VNConda\lib\site-packages\peewee.py", line 2888, in execute
return self.execute_sql(sql, params, commit=commit)
File "e:\VNConda\lib\site-packages\peewee.py", line 2882, in execute_sql
self.commit()
File "e:\VNConda\lib\site-packages\peewee.py", line 2666, in exit
reraise(new_type, new_type(*exc_args), traceback)
File "e:\VNConda\lib\site-packages\peewee.py", line 179, in reraise
raise value.with_traceback(tb)
File "e:\VNConda\lib\site-packages\peewee.py", line 2875, in execute_sql
cursor.execute(sql, params or ())
IntegrityError: NOT NULL constraint failed: dbbardata.vt_symbol
