Fixing UT_String compile issue for Houdini 14.
Fixing UT_String compile issue for Houdini 14.

UT_StringArray now returns a UT_StringHolder rather than a UT_String directly.

hradec/cortex,hradec/cortex,lento/cortex,hradec/cortex,goddardl/cortex,appleseedhq/cortex,goddardl/cortex,appleseedhq/cortex,lento/cortex,lento/cortex,goddardl/cortex,appleseedhq/cortex