Re: `@headitem` distorts vertical spacing

[Gavin Smith]

On Sat, Sep 03, 2022 at 11:51:32AM +0000, Werner LEMBERG wrote:
> 
> [texinfo version 2022-09-01.06]
> 
> 
> Consider the following example.
> 
> ```
> \input texinfo.tex
> 
> foo
> 
> @multitable {blubb} {bla}
> @item blubb @tab bla
> @item blubb @tab bla
> @end multitable
> 
> bar
> 
> @multitable {blubb} {bla}
> @headitem blubb @tab bla
> @item     blubb @tab bla
> @end multitable
> 
> baz
> 
> @bye
> ```
> 
> As can be seen, `@headitem` inserts extra vertical space, which looks
> ugly.

It should be fixed now, at the expense of a slightly worse error message
for an incorrectly nested @headitem.