Queue the stateChanged connection to prevent issues with Amarok's engine
controller.
On error Amarok's engine controller will delete the MediaObject, meaning
if the error state was emitted from the same thread it will destroy the
backend's MediaObject *while* it is doing something. By queuing the
connection the MediaObject can finish whatever it is doing before Amarok
starts doing nasty things to us.

Conflicts:
phonon/mediaobject.cpp