D5219: Use better description for size when size is not known

[Aleix Pol Gonzalez]

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

REPOSITORY
  R134 Discover Software Store

BRANCH
  size-description

REVISION DETAIL
  https://phabricator.kde.org/D5219

To: jgrulich, apol
Cc: plasma-devel, progwolff, lesliezhai, ali-mohamed, jensreuterberg, abetts, 
sebas, apol