fix: enhanced exception safety for our use of OpenColorIO (AcademySoftwareFoundation#5114)

https://opencolorio.readthedocs.io/en/latest/api/exceptions.html

"All functions in the Config class can potentially throw this
exception."

Oh dear, that is not something I previously fully understood the
implications of. This patch makes extra sure that there's try/catch
around every call to OCIO::Config methods. Some previously did, but some
that were less obvious that they might throw did not try/catch. No
matter how benign they look, I'm taking no chances now.

Signed-off-by: Larry Gritz <lg@larrygritz.com>
Signed-off-by: Vlad (Kuzmin) Erium <libalias@gmail.com>

Author: lgritz