Fixes cdlTransform.setXML segfault on malformed xml.
Fixes cdlTransform.setXML segfault on malformed xml.

Per dbr email.

AcademySoftwareFoundation/OpenColorIO,AcademySoftwareFoundation/OpenColorIO,AcademySoftwareFoundation/OpenColorIO,AcademySoftwareFoundation/OpenColorIO,AcademySoftwareFoundation/OpenColorIO