Render template file for the unregistered user.

    Args:
        error (str, default None): Optional error message.

    Returns:
        str: Template filled with data.

def render_unregistered(error=None):
    """
    Render template file for the unregistered user.

    Args:
        error (str, default None): Optional error message.

    Returns:
        str: Template filled with data.
    """
    return template(
        read_index_template(),
        registered=False,
        error=error,
        seeder_data=None,
        url_id=None,
    )