fix [#34104] vertex color: color select bug

changing the hue in a color picker on a panel when black/white was selected would fail because the hue from the previous state wasnt stored.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54294 954f8c5b-7b00-dc11-b283-0030488c597c