Better exception handling.
Additional Notes:
I'm now content with MASTER_GAIN being renamed to volume within JayLayer;
Volume is effectively a system volume, whereas MASTER_GAIN is value which
is given on to each track played. While gain is a better name, volume will
hopefully be more familier to those using this. This can always be changed
in a later commit.

Signed-off-by: Andrew <goobabtc@gmail.com>