Bitmask client QT library is incompatible with some desktop environments

How to reproduce:

• Login into an incompatible desktop environment: ** ubuntu 15.4 with MATE ** debian jessie with i3
• Download "Bitmask Client 0.9.0alpha10":https://downloads.leap.se/client/linux/internal/Bitmask-linux64-0.9.0alpha10.tar.bz2
• Unzip and run from terminal with @./bitmask -d --danger -l /tmp/bitmask.log@

Expected behaviour: client should launch wizard.

Observed behaviour: client crashes with: @Cannot mix incompatible Qt library (version 0x40806) with this library (version 0x40802)@

See full log attached.

(from redmine: created on 2015-06-17, closed on 2015-09-10, relates #7161 (closed), relates #7304 (closed))