When changing taskbar settings, applications in the systray quit.

Reproducible: Always
Steps to Reproduce:
1.  Open taskbar control panel
2.  Check pager, system tray, tasks randomly
3.  Uncheck those same options randomly
Actual Results:  
items that were minimized to the sys tray quit.

Expected Results:  
items in the sys tray should not quit, or xfce should give a warning before
closing them.