bug#37856: 27.0.50; 'next-error' advised with 'recenter' signals error when run from "*grep*" buffer

[Stefan Kangas <stefan@marxist.se>]

I get an error when advising 'next-error' with 'recenter'.

Steps to reproduce:
1. Under "emacs -Q", evaluate:
    (defun my-advice (&rest args)
      (recenter))
    (advice-add 'next-error :after #'my-advice)
2. M-x rgrep RET [... grep for something]
3. Run 'next-error' (M-g M-n) from the "*grep*" buffer.

Result: I get the error:
    recenter-top-bottom: ‘recenter’ing a window that does not display
current-buffer.

(I also get the error when I run it in the second window when
'next-error' would take you to a different file.)

Expected result: I get no error.

---

Backtrace:
Debugger entered--Lisp error: (error "‘recenter’ing a window that does
not display curre...")
  recenter()
  my-advice(nil)
  apply(my-advice nil)
  next-error(nil)
  funcall-interactively(next-error nil)
  #<subr call-interactively>(next-error nil nil)
  apply(#<subr call-interactively> next-error (nil nil))
  call-interactively@ido-cr+-record-current-command(#<subr
call-interactively> next-error nil nil)
  apply(call-interactively@ido-cr+-record-current-command #<subr
call-interactively> (next-error nil nil))
  call-interactively(next-error nil nil)
  command-execute(next-error)

---

This seems to be due to this code in window.c:

  /* For reasons why we signal an error here, see
     https://lists.gnu.org/r/emacs-devel/2014-06/msg00053.html,
     https://lists.gnu.org/r/emacs-devel/2014-06/msg00094.html.  */
  if (buf != current_buffer)
    error ("`recenter'ing a window that does not display current-buffer.");

This code was added here:
3da983f8c4 2014-06-06 Stefan Monnier * src/window.c (Frecenter):
Signal an error if window-buffer is not current-buffer.

---

In GNU Emacs 27.0.50 (build 1, x86_64-apple-darwin17.7.0, NS
appkit-1561.61 Version 10.13.6 (Build 17G8037))
 of 2019-10-21 built on Stefans-MBP
Repository revision: 0e6f4628d8fff53505e4399e71da9f531a64fff7
Repository branch: master
Windowing system distributor 'Apple', version 10.3.1561
System Description:  Mac OS X 10.13.6