Add missing const_cast
Add missing const_cast

I missed a const_cast and a pointer dereference when inlining the
code from shiboken2

Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master,Fat-Zer/FreeCAD_sf_master