Blender Git Loki

Fix T69497: Color Correction node ignores mask in certain cases

Happens when some of the color correction terms are mathematically
undefined: foe example, when pow() is to be calculated and the X
argument is negative.

There is no ground-truth result in such cases, so ignore such terms
entirely.

This is a generalization of D6696 from Jacques.

Differential Revision: https://developer.blender.org/D7966