bug#64759: Broken faces

[Juri Linkov]

>> Thanks, I confirm that '((t nil)) solves this problem.
>> If a nil value can't be supported for faces, then
>> let's use '((t nil)).
>
> What do you expect this to produce for the face attributes?

Let's see: when the definition is

  (defface display-time-date-and-time
    nil
    "Face for `display-time-format'."
    :group 'mode-line-faces
    :version "30.1")

then the customization buffer is

  Hide display-time-date-and-time face: [sample]
      State : NO CUSTOMIZATION DATA; not intended to be customized.
     Face for ‘display-time-format’.
     -- Empty face --
     Show All Attributes

But when the definition is

  (defface display-time-date-and-time
    '((t nil))
    "Face for `display-time-format'."
    :group 'mode-line-faces
    :version "30.1")

the customization buffer is

  Hide display-time-date-and-time face: [sample]
      State : STANDARD.
     Face for ‘display-time-format’.
     -- Empty face --
     Show All Attributes

Looks nice.  No strange error message about not intended to be customized.