bug#28575: 25.1; dired-do-find-regexp-and-replace error about previously deleted directory

[Teemu Likonen <tlikonen@iki.fi>]

Dired mode command "Q" (dired-do-find-regexp-and-replace) fails when
user has deleted a directory in the same Emacs session. Steps to
reproduce:

 1. Create test files:

    $ mkdir dir1 dir2
    $ touch dir1/file1 dir2/file2

 2. Start Emacs in dired-mode inside "dir1":

    $ emacs -Q dir1

    /home/dtw/tmp/dir1:
    total used in directory 0 available 16454160
    drwxr-xr-x 2 dtw  dtw  60 2017-09-24 16:02:00 .
    drwxrwxrwt 4 root root 80 2017-09-24 16:02:00 ..
    -rw-r--r-- 1 dtw  dtw   0 2017-09-24 16:02:00 file1

 3. Mark the "file1" with command "m" (dired-mark).

 4. Type command "Q" (dired-do-find-regexp-and-replace) and type any
    strings to the regexp and replace prompts.

 5. Go one directory up with command "^" (dired-up-directory).

    /home/dtw/tmp:
    total used in directory 4 available 16454160
    drwxrwxrwt  4 root root   80 2017-09-24 16:02:00 .
    drwxr-xr-x 61 dtw  dtw  4096 2017-09-24 15:42:49 ..
    drwxr-xr-x  2 dtw  dtw    60 2017-09-24 16:02:00 dir1
    drwxr-xr-x  2 dtw  dtw    60 2017-09-24 16:02:00 dir2

 6. Use "D" (dired-do-delete) to delete "dir1" (confirm with "yes"
    twice).

 7. Go to "dir2".

    /home/dtw/tmp/dir2:
    total used in directory 0 available 16454160
    drwxr-xr-x 2 dtw  dtw  60 2017-09-24 16:02:00 .
    drwxrwxrwt 3 root root 60 2017-09-24 16:03:32 ..
    -rw-r--r-- 1 dtw  dtw   0 2017-09-24 16:02:00 file2

 8. Mark the "file2" with command "m" (dired-mark).

 9. Type command "Q" (dired-do-find-regexp-and-replace) and enter some
    strings to regexp and replace prompts.

10. There will be the following error in the echo area and the
    *Messages* buffer:

        call-process-shell-command: Setting current directory: No such
        file or directory, ~/tmp/dir1/

    And the command "Q" can't be performed.