Fixed parabola calculation if vornonoi edge starts close to its location.
Fixed parabola calculation if vornonoi edge starts close to its location.

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