Handle invalid color channel values from pl/color-xyz-to-apply-rgb

[schellj]

With the existing pl/color-xyz-to-apply-rgb function, it's possible that pl/hex-color will generate a -0.0e+NaN color channel value for certain colors, such as those with zero B and/or G values. This will either result in an incorrect displayed color (e.g., in Emacs 26.2) or cause an error to be thrown (e.g., in Emacs 27.0). It's also possible that pl/color-xyz-to-apply-rgb will generate color channel values slightly outside of the valid range of 0.0 - 1.0, though that doesn't seem to cause any particular issues for Emacs.

Screenshots below from a test function comparing the changes in this PR with master and the core color-rgb-to-hex.

Emacs 26.2:

Emacs 27.0:

See https://gist.github.com/schellj/3a0ff288936322b59006d497bf607351 for the test function that I used for the screenshots above function (copy the PR pl/color-xyz-to-apple-rgb to schellj/color-xyz-to-apple-rgb).

I spent a long time (too much time) trying to figure out if the pl/color-xyz-to-apply-rgb matrix transformation was incorrect or if there was a better one, but that effort was unfruitful. Thus, I opted to just catch and handle the invalid color channel values.