App::Document: fix breakDependency
App::Document: fix breakDependency

Fixed breakDependency to handle repetitive entries inside
PropertyLinkList

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