The Kuwahara node produces NaNs if the pixels have a very high local
standard deviation and sharpness is also high. This is because the
weighted sum of the Kuwahara sectors can have a zero total weight, which
causes zero division. To fix this, we return the original color if the
total weight is zero.
Pull Request: https://projects.blender.org/blender/blender/pulls/128378
1b392ef016