[BUG] ox-texinfo no longer inserts menus if there is no content

[Jonas Bernoulli]

Hello,

(This came up in 878r9p1ntd.fsf@bernoul.li, on emacs-devel, but it
seems it fell through the cracks.)

If a section only has subsections but no content of its own, then
ox-texinfo no longer generates the section's menu (listing the
subsections).  And if the section additionally is part of an appendix,
then the subsections now use @subsection instead of @appendixsubsec.

I looked at the history of org and ox-texinfo.el in particular, but
could not find any code change that would explain that change in
behavior.  Org 9.6.8 still works as expected.

---- demo.org -------------------------------------------

* only subsections, no direct content
** sub 1
body
** sub 2
body
* A
:PROPERTIES:
:APPENDIX: t
:END:
** AA only subsections, no direct content
*** AAA
body

---- demo.texi with org release_9.6.8 -------------------

\input texinfo    @c -*- texinfo -*-

[...]

@node only subsections no direct content
@chapter only subsections, no direct content

@menu
* sub 1::
* sub 2::
@end menu

@node sub 1
@section sub 1

body

@node sub 2
@section sub 2

body

@node A
@appendix A

@menu
* AA only subsections, no direct content: AA only subsections no direct 
content. 
@end menu

@node AA only subsections no direct content
@appendixsec AA only subsections, no direct content

@menu
* AAA::
@end menu

@node AAA
@appendixsubsec AAA

body

@bye

---- demo.texi with org release_9.6.13-975-gb8d27bb4e ---

\input texinfo    @c -*- texinfo -*-

[...]

@node only subsections no direct content
@chapter only subsections, no direct content

@node sub 1
@section sub 1

body

@node sub 2
@section sub 2

body

@node A
@appendix A

@menu
* AA only subsections, no direct content: AA only subsections no direct 
content. 
@end menu

@node AA only subsections no direct content
@appendixsec AA only subsections, no direct content

@node AAA
@subsection AAA

body

@bye

---------------------------------------------------------

    bye;)
    Jonas