do not allow negative padding
do not allow negative padding


Former-commit-id: f72e869bc335ebe24974f4653a360d6c531b5e05
roryk/transrate,roryk/transrate,Blahah/transrate,cboursnell/transrate,Blahah/transrate,cboursnell/transrate,cboursnell/transrate,Blahah/transrate,roryk/transrate