Quitting `save-buffer' loses backup file

[Sven Joachim]

If saving a buffer with the current or preferred coding system is not
possible, Emacs displays a `*Warning*' buffer which tells to select a
safe coding system or to edit the buffer.  If you quit then, you will
lose the backup file for the buffer.  Take the following steps to
reproduce the problem:

$ echo "foo" > bar ; cp bar bar~
$ emacs -Q -f view-hello-file bar

In Emacs, in the "bar" buffer, type

M-x insert-buffer RET
C-x C-s

Emacs should display a '*Warning*' buffer now; type C-g to quit.
Now `buffer-backed-up' is t, but the backup file bar~ is gone. :-(

The problem seems to be long outstanding, I could also reproduce it
with Emacs 21.4.

In GNU Emacs 22.0.50.1 (i486-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 of 2005-11-19 on debian, modified by Debian
X server distributor `The X.Org Foundation', version 11.0.60802000