Response Validation Issue - "Cannot read property 'then' of undefined in modded.mung" about express-openapi-validator HOT 6 CLOSED

try {
    fn(json, req, res)
} catch ...

 try {
                fn(json, req, res)
                    .then(json => {
                    if (res.headersSent)
                        return;
                    // If null, then 204 No Content
                    if (json === null)
                        return res.status(204).end();
                    // If munged scalar value, then text/plain
                    if (json !== originalJson && isScalar(json)) {
                        res.set('content-type', 'text/plain');
                        return res.send(String(json));
                    }
                    return original.call(this, json);
                })
                    .catch(e => mung.onError(e, req, res, next));
            }