kubecolor: omit preset instead of declaring empty string (#2476)

Fixes: 74ee1ed ("kubecolor: init (#657)")
Link: #2476

Reviewed-by: Igor Rzegocki <ajgon@users.noreply.github.com>
Reviewed-by: 0xda157 <da157@voidq.com>

Author: trueNAHO

modules/kubecolor/hm.nix

@@ -1,9 +1,8 @@
-{ mkTarget, ... }:
+{ mkTarget, lib, ... }:
 mkTarget {
   config = [
     ({ polarity }: {
-      programs.kubecolor.settings.preset =
-        if polarity == "either" then "" else polarity;
+      programs.kubecolor.settings.preset = lib.mkIf (polarity != "either") polarity;
     })
     ({ colors }: {
       programs.kubecolor.settings.theme = with colors.withHashtag; {