D9504: Show that the last check failed if no updates available

[Jan Grulich]

jgrulich accepted this revision.
This revision is now accepted and ready to land.

REPOSITORY
  R623 Plasma PackageKit Updater

BRANCH
  fixes

REVISION DETAIL
  https://phabricator.kde.org/D9504

To: fvogt, lukas, jgrulich
Cc: ngraham, plasma-devel