def convert_parameters_to_None(config):
    """Convert parameters whose value is "" into None.

    Parameters
    ----------
    config: dict
        Dictionary containing all the parameters of the App.

    Returns
    -------
    config: dict 
        Dictionary with parameters converted to None where needed.   

    """

    # Convert all "" to None when the App runs on BL
    tmp = dict((k, None) for k, v in config.items() if v == "")
    config.update(tmp)

    return config