single-key-description doesn't like unknown characters

[Christopher Stacy]

In GNU Emacs 22.0.50.1 (powerpc-apple-darwin8.3.0)
 of 2005-12-04 on mini.local
X server distributor `Apple Computers', version 10.4.6
configured using configure '--enable-carbon-app=/Applications'
 '--prefix=/Applications/Emacs.app/Contents/Resources' '--with-carbon'
 '--without-x' 'CFLAGS=-DUSE_ATSUI -fast -mcpu=7450' 
'CPPFLAGS=-DOLDROUTINENAMES':

I bound [1048673] to a function and tried to do describe-key-briefly on it.
The input of this funny character for the "C-h c" was accomplished
through key-translation-map.   (This is a hack in which I am mapping
certain characters into a funny UNICODE space, the Plane Sixteen PUA
I hope, and then binding commands to those.   Don't ask why...)
Anyway, the bug is that single-key-description blows up with
the error: "Invalid character: 04000141, 1048673, 0x100061".

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t