xbmc/xbmc — pull request #2129 by ulion (2013-01-28 01:02:23+00:00)
Title: paplayer handle prepare stream failure.

I've encountered a crash in gdb after log message:
```
PAPlayer::PrepareStream - Failed to get IAEStream
```

what cause crash is at line in PAPlayer::ProcessStream with si->m_stream == NULL:
```
si->m_stream->RegisterAudioCallback(m_audioCallback);
```

I checked only place called PrepareStream is in PAPlayer::QueueNextFileEx where did not check failure, so here is the fix for it, please check whether it is correct..