fix a crash seen in PSM by making sure a zero-length attribute zeroes the item inheriting it
fix a crash seen in PSM by making sure a zero-length attribute zeroes the item inheriting it

nmav/nss,ekr/nss-old,ekr/nss-old,nmav/nss,ekr/nss-old,nmav/nss,nmav/nss,ekr/nss-old,ekr/nss-old,nmav/nss,nmav/nss,nmav/nss,ekr/nss-old,ekr/nss-old