UnboundLocalError: local variable 'hist' referenced before assignment

[jiedxu]

    def record(word, path=_path):
        """Append queried word in a yaml file in lowercase format.
    
        If the path is directed to yaml file, there will be three
        situations. When there is no such file, we create a new one
        according to the specified file name and write the word. When the
        file does exist, we read its content first.
    
        Args:
            word (str): to be appended at the end of the yaml file.
            path (str): to the yaml file.
    
        Raises:
            ValueError: when the path is not to a yaml file.
        """
        if not path.endswith(".yaml"):
            raise ValueError(f"{path} is not a path to yaml file.")
    
        if not pathlib.Path(path).is_file():
            with open(path, "w") as f:
                yaml.safe_dump([word], f)
        else:
            with open(path, "r") as f:
                try:
                    hist = yaml.safe_load(f)
                except yaml.YAMLError as exc:
                    logger.exception(exc)
    
>           if hist is None:
E           UnboundLocalError: local variable 'hist' referenced before assignment

src/cmdict/history.py:41: UnboundLocalError