Revert "Dealing with undefined curves in drillability checking."
Revert "Dealing with undefined curves in drillability checking."

This reverts commit bba1c4871db42bed98992bd1dca764ecd42e98b7.

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