bug#29923: [PATCH] Skip writing empty abbrev tables

[Noam Postavsky]

Allen Li <darkfeline@felesatra.moe> writes:

> The system abbrev omitting worked (if readable is nil); it's
> implemented in abbrev--write.
> However, that doesn't allow us to skip writing a table if it only
> contains system abbrevs;
> we'll still see a table with abbrevs, write the opening of the
> define-abbrev-table form,
> and then realize in abbrev-write that all of the abbrevs are system abbrevs.

Ah, it would be good to have this information in the commit message, as
the patch is a bit confusing to read otherwise.

> I noticed a bug in my patch where it would skip system abbrevs if
> readable was non-nil
> when it did not skip system abbrevs previously.  I fixed this and also
> fixed the docstring
> to match what I believe is the intended behavior.

Okay, looks good, could you please enhance the commit message as
mentioned above?