Re: Apparently incorrect changes to custom-magic-alist.

[Richard Stallman]

      you have edited the value as text, but you have not set the %c." "\
    ! you have edited something in this group, but not set anything yet.")
          (set "+" custom-set-face "\
      you have set this %c, but not saved it for future sessions." "\
    ! you have set something in this group, but not saved anything yet.")
          (changed ":" custom-changed-face "\
      this %c has been changed outside the customize buffer." "\
      something in this group has been changed outside customize.")
    --- 1671,1680 ----
      the value displayed for this %c is invalid and cannot be set.")
          (modified "*" custom-modified-face "\
      you have edited the value as text, but you have not set the %c." "\
    ! you have edited something in this group, but not set it.")

That string doesn't mean what you think it means.

I will make another change to deal with the error that 
you have shown.