Comment # 1 on bug 1165983 from Michael Andres

That's IMO an issue of PackageKit backend in the first place. Even if TW
downgraded libzypp from 17.23.1-3.1 (your screenshot) to 17.23.1-1.1 (in
http://download.opensuse.org/tumbleweed/repo/oss/). It's pretty legal for a
package to have no updateCandidateObj().

PK backend should be able to handle this -> assigning to maintainer
(gnome-maintainers)