[lang] Color -asHSV: Achromatic colors return nan

[dyfer]

Purpose and Motivation

Achromatic colors (black, white, grey) return nan from Color -asHSV method. That makes calculations problematic. Correct me if I'm wrong, but I believe that 0 is an appropriate value for hue and saturation in these cases.

//before fix
Color.black.asHSV
// -> [ nan, nan, 0.0, 1.0 ]
Color.white.asHSV
// -> [ nan, 0.0, 1.0, 1.0 ]
Color.grey.asHSV
// -> [ nan, 0.0, 0.5, 1.0 ]

//after fix
Color.black.asHSV
// -> [ 0.0, 0.0, 0.0, 1.0 ]
Color.white.asHSV
// -> [ 0.0, 0.0, 1.0, 1.0 ]
Color.grey.asHSV
// -> [ 0.0, 0.0, 0.5, 1.0 ]

//also:
Color.hsv(*Color.black.asHSV) == Color.black; //false before fix, true after fix

Types of changes

• Bug fix
• Breaking change (?)

To-do list

• Code is tested
• All tests are passing (does this need tests?)
• Updated documentation (documentation for this change is not needed)
• This PR is ready for review

[mossheim]

Thanks! Please rebase this against 3.10 -- see our contributor's guide for more information.

[mossheim]

Actually, let's merge this to develop as it's a breaking change. I think this is the correct fix -- according to our documentation, it should return values in the range [0, 1] -- but it doesn't strictly preserve old behavior.