bug#64024: 29.0.91; `emoji-insert` shows me confusing empty lists

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

>>     % src/emacs -Q
>>     M-x emoji-insert RET
>>     s s
>> 
>> I expect at this point to see a list of "smiling Smiley" emojis
>> displayed in the small bottom window, but instead that window is empty
>> (there's just a one-pixel-thick line about one-char wide at the very
>> top-left) and it sits there.
>
> I cannot reproduce this, neither in the 29.0.91 pretest nor in the
> current emacs-29 branch.  I get the behavior you expected: a small
> window at the bottom of the frame showing some smileys.

I think the problems only appear if the list of emojis becomes empty.

>> Side note: during this `emoji-insert` interaction, I only see
>> black&white emojis, so maybe this is linked to some compilation option
>> I used which prevents the use of color emojis, tho I don't know what
>> that option would be.
> Do you have Noto Color Emoji font installed?

Here I get the normal/expected behavior and I do have
`fonts-noto-color-emoji` installed but on the machine where I see the
problem that package is indeed not installed.

So I guess to reproduce the problem you need to use a machine that
has sufficiently few fonts that the list of emojis becomes empty in the
category that you select (such as "smiling smileys").


        Stefan