bug#46990: 28.0.50; popup menu not navigable via arrow keys on lucid build

[Visuwesh]

[திங்கள் ஜூன் 20, 2022] Po Lu via "Bug reports for GNU Emacs, the Swiss army 
knife of text editors" wrote:

> Visuwesh <visuweshm@gmail.com> writes:
>
>> `installation-directory' is non-nil for me yet I can navigate the menus
>> with the keyboard.
>>
>>     installation-directory is a variable defined in ‘C source code’.
>>
>>     Its value is "/home/viz/lib/ports/emacs/"
>
> Whether or not the keyboard must be grabbed for key navigation to work
> depends on various details of your system, and whether or not the mouse
> pointer happens to be on top of the menu bar at the time (if you're
> running an XInput 2 build), so I'm not surprised that it works for some
> people regardless of the value of GRAB_KEYBOARD.

Right, point noted.