libarea: fix arc fitting bug
libarea: fix arc fitting bug

Bug introduced in fb16c867ed8a9fb7be7dabd6d98d4dc1c04fc27a

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