fixes 0002304: Duplicate multi selection of sketch element produces many sketches
fixes 0002304: Duplicate multi selection of sketch element produces many sketches

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