fix possible error with accessing nonexistent setting

        return

    valtype = type(opts.data_labels[key].default)

    oldval = opts.data[key]

    oldval = opts.data.get(key, None)

    opts.data[key] = valtype(value) if valtype != type(None) else value

    if oldval != value and opts.data_labels[key].onchange is not None:

        opts.data_labels[key].onchange()