Prevent Canceled FileChooser from calling print

Summary: Changes from: https://phabricator.kde.org/R231:f72448828270d266acf4fbde69d09bc648337b7f Create an error dialog if the print function is called with empty filename. This checks that the dialog was accepted before sending the filename to the print function preventing the error message from showing.

Reviewers: patrickelectric, tcanabrava, laysrodrigues

Reviewed By: patrickelectric, tcanabrava

Subscribers: Atelier

Tags: Atelier

Differential Revision: https://phabricator.kde.org/D17117