bug#30938: 27.0; `dired-do-create-files' etc.: do NOT always raise error if no files

[Eli Zaretskii]

> Date: Sun, 25 Mar 2018 09:36:08 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> 
> The bug is that calls to `dired-get-marked-files' have been changed all
> over the place to systematically pass a non-nil value for optional arg
> ERROR.  In general, this is completely inappropriate when the command
> invoking `dired-get-marked-files' is not called interactively.
> 
> There is NO reason to suppose that a `user-error' occurred when a given
> command is invoked non-interactively.
> 
> The logic behind this change is wrong - much too simplistic.  A non-nil
> ERROR arg should perhaps be passed when called from some commands, but
> typically only when such a command is called interactively.  Only then
> might Emacs legitimately assume (and even this is arguable, in general)
> that the user has committed an error.

Please provide at least one example (preferably more than one) of a
real-life use case where these changes get in the way.