如图所示，已通过直达api订阅到XINA50股指的CN2006合约，数据库无数据，直接实盘提示行情订阅失败，找不到合约CN2006，该如何解决外盘实盘时的此类报错呢？望解答
报错代码：
CN2006: 触发异常已停止
Traceback (most recent call last):
File "C:\Users\78405\Desktop\vnpy_20200608\vnpy\app\cta_strategy\engine.py", line 602, in call_strategy_func
func()
File "C:\Users\78405\Desktop\vnpy_20200608\vnpy\app\cta_strategy\strategies\atr_rsi_strategy.py", line 66, in on_init
self.load_bar(10)
File "C:\Users\78405\Desktop\vnpy_20200608\vnpy\app\cta_strategy\template.py", line 245, in load_bar
use_database
File "C:\Users\78405\Desktop\vnpy_20200608\vnpy\app\cta_strategy\engine.py", line 535, in load_bar
symbol, exchange = extract_vt_symbol(vt_symbol)
File "C:\Users\78405\Desktop\vnpy_20200608\vnpy\trader\utility.py", line 27, in extract_vt_symbol
symbol, exchange_str = vt_symbol.split(".")
ValueError: not enough values to unpack (expected 2, got 1)
