bug#51421: 28.0.60; describe-key fails from menu item: "Position not in text area of window"

[Andy Moreton <andrewjmoreton@gmail.com>]

Hi,

 From emacs -Q, type "C-h k" then select a menu item with the mouse
e.g. "File" then "Close". This reports "Position on in text area of
window".

On emacs 27.2 this correctly describes the key binding for the menu
item. It fails on the emacs-28 and master branches.

     AndyM

In GNU Emacs 28.0.60 (build 2, x86_64-w64-mingw32)
  of 2021-10-25 built on QUIETUS
Repository revision: 284c77eeb60bf21d8811f011902cd56f4aeaddca
Repository branch: emacs-28
Windowing system distributor 'Microsoft Corp.', version 10.0.19043
System Description: Microsoft Windows 10 Pro (v10.0.2009.19043.1288)

Configured using:
  'configure --prefix=c:/emacs/28.0.60/mingw64-x86_64-O2-native
  --cache-file=/c/emacs/git/emacs/emacs-28/build/mingw64-x86_64-O2-native/config.cache
  --without-compress-install --without-dbus --with-gif --with-gnutls
  --without-imagemagick --with-jpeg --with-json --with-lcms2
  --with-modules --with-native-compilation --with-png --without-pop
  --with-rsvg --with-tiff --with-xml2 --with-xpm --enable-checking
  'ac_cv_search___gmpz_roinit_n=-Wl,--push-state,-static -lgmp
  -Wl,--pop-state' 'CPPFLAGS= -DNO_SHLWAPI_ISOS=1' 'CFLAGS= -O2 -g3
  -gdwarf-4 -fdiagnostics-color=never''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND THREADS TIFF TOOLKIT_SCROLL_BARS
XPM ZLIB