If there's no configured SoundFont bank, or if the selected bank has
gone missing, and the user has configured the player to use the
FluidSynth driver, fall back to the system DLS Synthesizer, which has
its own Roland bank to fall back on if unconfigured.
Also, whether falling back, or already on an AU synthesizer, don't fail
if there's no bank configured or found. DLS doesn't explicitly require a
bank, and most other synthesizers of interest would not require a bank
either.
Signed-off-by: Christopher Snowhill <kode54@gmail.com>
3c35cf1037