troubleshoot Define North optional param property

[colinlsmatthews]

        protected override void RegisterInputParams(GH_Component.GH_InputParamManager pManager)
        {
            pManager.AddGenericParameter("True North", "T", "Input to define true north direction", GH_ParamAccess.item);
            pManager.AddGenericParameter("Project North", "P", "Input to define project north direction", GH_ParamAccess.item);
            pManager[0].Optional = true;
            pManager[1].Optional = true;
        }