Comment 34 for bug 444563

And even that wasn't enough to stop all the warnings. Apparently lvdisplay doesn't set an error code if there were zero results. The following should catch that situation and stop the last of it:

ENV{DM_UUID}=="LVM-*", PROGRAM="/bin/sh -ec 'set -- $(lvm lvdisplay -C -o vg_name,lv_name --noheadings /dev/$name); echo ${2+$1/$2}'", SYMLINK+="$result"