Fixed null pointer exception when this.player.Source is null in the startPlaying method of Audio player. Error callback now works multiple times.
Merge branch 'topic' of git://github.com/bennmapes/cordova-wp7
<cordova> becomes <widget>
Merge pull request #3 from purplecabbage/CB-2323

<cordova> becomes <widget>
CB2444 - events not fired