bug#51076: 28.0.60; Null dereference warning with nox build in make_lispy_position

[Eli Zaretskii]

> Date: Thu, 07 Oct 2021 12:35:24 +0100
> From:  "Basil L. Contovounesios" via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> In file included from keyboard.c:29:
> keyboard.c: In function ‘make_lispy_position’:
> frame.h:949:35: warning: null pointer dereference [-Wnull-dereference]
>   949 | #define FRAME_TAB_BAR_LINES(f) (f)->tab_bar_lines
>       |                                ~~~^~~~~~~~~~~~~~~
> keyboard.c:5134:10: note: in expansion of macro ‘FRAME_TAB_BAR_LINES’
>  5134 |       && FRAME_TAB_BAR_LINES (f) > 0
>       |          ^~~~~~~~~~~~~~~~~~~
> 
> AFAICT the preceding condition '!FRAME_WINDOW_P (f)' will always be true
> in a nox build

Yes, but what about a build with X support that displays a TTY frame?

I installed a trivial fix.