Fix CMYK output on black

[felixdorn]

Reproduce:

• Open https://duckduckgo.com/?q=%23000000
• Launch hyprpicker with the cmyk format

  hyprpicker --no-fancy --format cmyk 

• Click in the black circle
• Observe:

  -nan% -nan% -nan% 0%

Fix:

The current implementation does not handle the case where K = 0, which causes a divide by zero error when computing c, m, y which are of the form [expr] / K.

In this case, setting K = 1 is a correct way to handle this edge case.