dropout

Results 2 issues of dropout

### Documented behaviour Updating the UI in response to state changes. ### Actual behaviour SwithAudioHandler.playbackState does not propagate errors. In a SwitchAudioHandler implementation the inner handlers cannot propagate errors with...

When using SwitchAudioHandlers, inner AudioHandler's were unable to propagate errors to SwitchAudioHandler [#986](https://github.com/ryanheise/audio_service/issues/986) ## Pre-launch Checklist - [x] I read the [CONTRIBUTING.md] and followed the process outlined there for submitting...