bug#24774: 26.0.50; Menu display navigation commands

[Gregory Heytings]

> > I get nil too with C-j, C-x C-e, and M-:, and regardless of '-nw'.
> >
> > > Maybe it's system-dependent?  What Emacs configuration is the one 
> > > where you get the above?
> >
> > In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 
> > 1.16.0, Xaw3d scroll bars) of 2021-02-23 built on tia
>
> So maybe this is specific to GTK builds?

I just tried on several GTK builds (of Emacs 26, 27 and 28) and they all 
return nil.