add warnings if some rows of the gradient matrix is empty in NonlinearProgram
add warnings if some rows of the gradient matrix is empty in NonlinearProgram

billhoffman/drake,manuelli/drake,thientu/drake,sheim/drake,billhoffman/drake,psiorx/drake,sheim/drake,billhoffman/drake,psiorx/drake,manuelli/drake,thientu/drake,billhoffman/drake,psiorx/drake,manuelli/drake,psiorx/drake,psiorx/drake,billhoffman/drake,tkoolen/drake,edowson/drake,tkoolen/drake,scottviteri/drake,edowson/drake,thientu/drake,crogers3/drake,thientu/drake,thientu/drake,astrorog/drake,hanssusilo/drake,thientu/drake,sheim/drake,crogers3/drake,sheim/drake,hanssusilo/drake,astrorog/drake,sheim/drake,sheim/drake,crogers3/drake,crogers3/drake,scottviteri/drake,manuelli/drake,hanssusilo/drake,tkoolen/drake,crogers3/drake,crogers3/drake,astrorog/drake,astrorog/drake,tkoolen/drake,edowson/drake,astrorog/drake,scottviteri/drake,scottviteri/drake,hanssusilo/drake,astrorog/drake,astrorog/drake,edowson/drake,crogers3/drake,thientu/drake,hanssusilo/drake,manuelli/drake,billhoffman/drake,billhoffman/drake,manuelli/drake,edowson/drake,edowson/drake,edowson/drake,hanssusilo/drake,billhoffman/drake,hanssusilo/drake,psiorx/drake,sheim/drake,psiorx/drake,edowson/drake,psiorx/drake,scottviteri/drake,tkoolen/drake,tkoolen/drake,sheim/drake,scottviteri/drake,tkoolen/drake,manuelli/drake,crogers3/drake,hanssusilo/drake,scottviteri/drake