[21.1]: mouse-1 on header-line in *info* barfs and gotos node

[Marshall, Simon]

In GNU Emacs 21.1.1 (sparc-sun-solaris2.6, GNU/LessTif Version 2.1
Release 0.93.3)
 of 2001-10-23 on ashanti
configured using `configure  --prefix=/rvcarma/marshals/slash/usr/local
--x-includes=/usr/openwin/include:/rvcarma/marshals/slash/usr/local/incl
ude:/rvcarma/marshals/slash/usr/local/include/X11
--x-libraries=/usr/openwin/lib:/rvcarma/marshals/slash/usr/local/lib:/rv
carma/marshals/slash/usr/local/lib/X11 --with-x-toolkit=motif'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: en_UK
  value of $LC_CTYPE: en_UK
  value of $LC_MESSAGES: C
  value of $LC_MONETARY: en_UK
  value of $LC_NUMERIC: en_UK
  value of $LC_TIME: en_UK
  value of $LANG: en_UK
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

emacs -q
C-h i m Emacs RET

takes you to the Emacs manual.  ok.

now mouse-1 on the "Top" in "Up: Top" in the header-line.
Emacs barfs (though it does then takes you to the Top node).

The barf is:

Debugger entered--Lisp error: (error "Cannot move header-line at the top
of the frame")
  signal(error ("Cannot move header-line at the top of the frame"))
  error("Cannot move header-line at the top of the frame")
  mouse-drag-header-line((down-mouse-1 (#<window 3 on *info*>
header-line (260 . 3) 21115583 (#("Next: Distrib,  Prev: (dir),  Up:
(dir)" 0 6 ... 6 13 ... 13 16 nil 16 22 ... 22 27 ... 27 30 nil 30 34
... 34 39 ...) . 36))))
  call-interactively(mouse-drag-header-line)

I can understand a barf is appropriate (assuming that dragging the
header-line makes sense in some contexts), and I can understand going
to the Top node is appropriate, but doing both doesn't seem right.

Simon.