MuseScore freezes when switching driver to PulseAudio if backend is not running

Ubuntu 13.04 32-bit, MuseScore 2 commit fc6fe02.

Reproduce:
1. Make sure that pulseaudio is not running.
2. Start MuseScore with any audio driver.
3. Go to Preferences -> I/O, change driver to PulseAudio, press "OK"

Expected behaviour: connection error in logs, Preferences window closes.
Actual behaviour: connection error in logs, MuseScore freezes (infinite loop).