notes,
- Use our own callback which doesnt exit() blender.
- Hard coded 'MONOSCNR.ICM' is bad, should this be a user preference or stored per image?
- imb->crect was being set to imb->rect in some cases, disable this because its possible 'rect' gets reallocated and crect becomes freed memory.
- when crect cant be created draw pink checkers, so users dont get confused if color correction isnt working. (previously would draw the uncorrected image, if it didnt crash)
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