Fixes errors in maya -batch trying to create a callback for non-existent UI.
Fixes errors in maya -batch trying to create a callback for non-existent UI.


appleseedhq/cortex,danieldresser/cortex,appleseedhq/cortex,hradec/cortex,goddardl/cortex,davidsminor/cortex,goddardl/cortex,lento/cortex,goddardl/cortex,appleseedhq/cortex,hradec/cortex,danieldresser/cortex,davidsminor/cortex,danieldresser/cortex,lento/cortex,davidsminor/cortex,danieldresser/cortex,lento/cortex,davidsminor/cortex,hradec/cortex