Fix of the issue that improper check
of dr_mp3 library initialization
success could result in double-free
of library internals in case
initialization was unsuccessful.
* Fix of the issue that 'File has been
deleted' popup would show in Relaxation
app at the end of playback if the
playback was paused at least once,
even though the file wasn't actually
deleted.
* Added very basic audio decoder error
handling and propagation mechanism.
* Minor refactor around several
audio-related parts.
