bug#64543: [PATCH] package-report-bug: don't fail on custom groups defined by eval

[Eli Zaretskii]

> From: Philip Kaludercic <philipk@posteo.net>
> Cc: sbaugh@janestreet.com,  sbaugh@catern.com,  64543@debbugs.gnu.org
> Date: Sat, 15 Jul 2023 07:40:01 +0000
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> Eli, would it be OK to push this to emacs-29, as this is a bug in the
> >> existing code?  Most of the changes are indentation/whitespace changes
> >> anyway.
> >
> > I don't understand the cases in which this bug happens, and so cannot
> > make the decision.  
> 
> Spencer gave this example:
> 
>   >> Previously we just assumed that the car of an element of
>   >> custom-current-group-alist was a filename.  But actually it can be nil
>   >> if a custom group was defined by just evaling Lisp.
>   >
>   > Where is this behaviour documented?  I couldn't reproduce it with a
>   > simple experiment.
> 
>   To reproduce:
>   M-: (defgroup mygroup nil "my group") RET
> 
> The patch would ensure that if groups like these are defined (which
> might happen by mistake), then `package-report-bug' will remain robust
> and not fail due to a unrelated issue.

Is this case important enough to make this change so late in the
pretest?  Spencer, how did you bump into this situation in Real Life?