Sometimes happens to get a NullReferenceException in method:

public T MarshalJsValue<T>(JsInstance value)

The problem arises if the "value" parameter is null.

A brute workaround could be a check at the very beginning of the method (but I think that a deeper problem is involved somewhere else if that variable occurs to be "null"):

    public T MarshalJsValue<T>(JsInstance value)
    {
        if (value == null)
        {
            T result = (T)Convert.ChangeType(null, typeof(T));
            return result;
        }