bug#8792: 23.3; EasyPG: do not create empty buffers if file cannot be read

[Roland Winkler]

If a gpg-encrypted file cannot be read for whatever reason (see,
e.g., bug#8791) one gets the error message

  File exists, but cannot be read

and just an empty buffer. This empty buffer can be dangerous because
emacs believes it is really visiting the file. Say, if this empty
buffer gets modified and saved automatically, this will just
override the original file. I suggest that EasyPG should be more
cautious here (or: provide a means to be more cautious if desired).


In GNU Emacs 23.3.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.12.9)
 of 2011-06-02 on lukas

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: C
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: en_GB.utf8
  value of $LANG: en_US.ISO-8859-15
  value of $XMODIFIERS: nil
  locale-coding-system: iso-latin-9-unix
  default enable-multibyte-characters: t