assistant: don't crash when run as non-gui in mac/linux
assistant: don't crash when run as non-gui in mac/linux

Also don't use obsolete QApplication constructor.

Change-Id: Ibe172e13caeccb08a388b0fe8ebbddf25c5ca0ec
Reviewed-by: Karsten Heimrich <81d67632fe4bf9afb88a400b41aa25e19a1d2a12@nokia.com>

mer-qt/qttools,mer-qt/qttools,mer-qt/qttools,mer-qt/qttools,mer-qt/qttools,mer-qt/qttools