fix: Frame fails when a type with an optional or nullable field is used

[charsleysa]

Types such as the following currently fail when trying to make the nested fields selectively discloseable:

type PID = {
    given_name: string;
    address?: {
        country: string;
    }
};

const disclosureFrame: DisclosureFrame<PID> = {
    _sd: ['given_name'],
    address: {
        _sd: ['country']
    }
};

Signed-off-by: Stefan Charsley charsleysa@gmail.com

[lukasjhan]

LGTM. Thank you for the PR :)

[cre8]

Thank you @charsleysa for the fix! The latest version was released with it some minutes ago.