This fails if playing an item outside of the library.

```
21:29:45 T:2942651248  NOTICE: [trakt] [traktPlayer] onPlayBackStarted() - {"id":1,"jsonrpc":"2.0","result":{"item":{"label":"Game of thrones s01e01.mkv","type":"unknown"}}}
21:29:45 T:2942651248   ERROR: EXCEPTION Thrown (PythonToCppException) : -->Python callback/script returned the following error<--
                                             - NOTE: IGNORING THIS CAN LEAD TO MEMORY LEAKS!
                                            Error Type: <type 'exceptions.KeyError'>
                                            Error Contents: ('id',)
                                            Traceback (most recent call last):
                                              File "/home/xbmc/.xbmc/addons/script.trakt/notification_service.py", line 117, in onPlayBackStarted
                                                self.id = result["result"]["item"]["id"]
                                            KeyError: ('id',)
                                            -->End of Python script error report<--
```