Fix broken reloading and broken layout changing due to lost filename

Summary: Fixup for 67489cf6764f53e343d47609ead354388f948a5b

Test Plan:
Reload (F5) and changing the layout algorithm no longer results in error
message about not being able to load "".

Reviewers: ltoscano, kleag

Reviewed By: kleag

Differential Revision: https://phabricator.kde.org/D7932