Path: Add error for incorrect open-edge usage
Path: Add error for incorrect open-edge usage

When profiling open edges, the user must currently select a top edge and then set the Final Depth manually to a value below the selected edge(s).
This fix provides the user with feedback for the empty path generated.
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