Fix occasional freezing when reaching the end of an audio file

[mpharoah]

Application can apparently freeze if it's left at the end of an audio file for an extended period of time. Maybe also happens if just left paused?

[mpharoah]

Might be because I'm not iterating the PulseAudio mainloop while the audio is paused. Perhaps PulseAudio does not expect there to be an unbounded amount of time between mainloop iterations? I should also make sure there aren't events still piling up while the mainloop isn't iterating.