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

[Po Lu]

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.