D9149: Allow running the tool without a display

[Adriaan de Groot]

adridg added a reviewer: mart.

REPOSITORY
  R119 Plasma Desktop

REVISION DETAIL
  https://phabricator.kde.org/D9149

To: adridg, #plasma, mart
Cc: plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, 
abetts, sebas, apol, mart