Added a condition trying to avoid the problem described in issue 448 (https://github.com/zhouhaoyi/Informer2020/issues/448) (TypeError: 'NoneType' object is not subscriptable). The problem occurred because of the self.freq is None and the original code was trying to index into the None type.
Added a condition trying to avoid the problem described in issue 448 (https://github.com/zhouhaoyi/Informer2020/issues/448) (TypeError: 'NoneType' object is not subscriptable). The problem occurred because of the self.freq is None and the original code was trying to index into the None type.