bug#56605: editing a file from an archive can die with a message that says nothing to a random user

[Paul Pogonyshev]

GNU Emacs 28.1.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 2.24.33, cairo version 1.16.0) of 2022-05-24

1. Open any archive (tested with JAR and TAR)

2. Open any file from said archive (in a separate buffer)

3. Switch to the archive buffer and kill it

4. Go to the file buffer from step 2, modify it and try to save

5. Saving dies with "Selecting deleted buffer" error

I'm not sure what the behavior should be (most user-friendly: silently reopen the archive if it still exists), but it certainly shouldn't be "I will die with some internal error, let user decifer what that means".

Paul