Users with an external DAC may connect and disconnect the device and, while Phonon fallback to any alternative device available, kmix doesn't change the Master Channel and actually the system tray applet seems to crash.

It may happen in different scenarios, but mine is the following:
I have a notebook and a DAC connected to my dockstation. When I disconnect my note, any current music continues to play in built-in speakers. The problem is that volume adjust brakes.

Reproducible: Always

Steps to Reproduce:
1. Connect a DAC and play a song
2. DIsconnect the DAC, it will continue to play in audio card
3. Try to change volume through applet or keyboard keys
Actual Results:  
I'm not able to change volume, unless I set Master Channel back to audio card

Expected Results:  
kmix should notice that a audio device is disconnected and fallback to another available device

Some relation with #155262