def get_upload_folder_structure(file_name):
    """
    Return the structure in the upload folder used for storing and
    retrieving uploaded files.

    Two folder levels are created based on the filename (UUID). The
    first level consists of the first two characters, the second level
    consists of the third character of the uuid.

    Example: ``9cd7b281-2c70-42eb-86ec-e29fc755cc1e.jpg`` is stored to
    ``9c/d/9cd7b281-2c70-42eb-86ec-e29fc755cc1e.jpg``.

    Args:
        file_name (str): The name of the file.

    Returns:
        list. A list of the folders or an empty list if there was a problem with
        the file name.
    """
    try:
        return [file_name[0:2], file_name[2:3]]
    except TypeError:
        return []