bug#13522: 24.2; save-buffer removes edited file under some conditions

[Glenn Morris]

Vincent Lefevre wrote:

> 1. Create a file with: printf "\x80" > file
> 2. Open the file under X Window with: emacs -Q file
> 3. Modify the file e.g. by adding a space.
> 4. Type C-x C-s
>    At this point, Emacs asks the user to select a coding system.
> 5. Type C-c in the terminal to kill Emacs.
>
> The result is that the file "file" is no longer there!

I can't reproduce this with 24.2.
Here I have both "file" and "#file", no "file~".

> Actually there is a backup. Here it is easy to see (file~), but