bug#55834: 29.0.50; gnus: Z n in digest group does not catch up

[Sam Steingold <sds@gnu.org>]

`Z n` (gnus-summary-catchup-and-goto-next-group) in digest groups no
longer catches up the parent group.

Steps to reproduce:
in gnus, enter "gmane.comp.security.risks" on nntp:news.gwene.org and do
`C-d` (gnus-summary-enter-digest-group) on a the only unread message.
In the newly created digest *Summary* buffer, do `Z n` - this will catch
up the digest and move you to the next group.
However, the "gmane.comp.security.risks" group will remain un-caught-up,
i.e., the *Groups* buffer shows it as if it has unread messages.

Expected behavior (observed until about a month ago?):
`Z n` should catch up the digest and move on to the parent group; if
there are no unread message (my case) it should also catch this one up
and move to the next group with unread messages, marking this group in
*Groups* as empty (this is the regression: it did so before, but not
anymore).



In GNU Emacs 29.0.50 (build 1, x86_64-apple-darwin21.4.0, NS appkit-2113.40 Version 12.3.1 (Build 21E258))
 of 2022-06-07 built on 3c22fb11fdab.ant.amazon.com
Repository revision: 3864308c20deb69e7b75420377a3b86716215dd3
Repository branch: master
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.3.1

Configured using:
 'configure --with-imagemagick --with-mailutils --with-ns
 PKG_CONFIG_PATH='

Configured features:
ACL GIF GMP GNUTLS IMAGEMAGICK JPEG JSON LCMS2 LIBXML2 MODULES NOTIFY
KQUEUE NS PDUMPER PNG SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS WEBP ZLIB

Important settings:
  value of $LANG: C
  locale-coding-system: utf-8-unix

Major mode: Group

Minor modes in effect:
  shell-dirtrack-mode: t
  gnus-undo-mode: t
  global-edit-server-edit-mode: t
  winner-mode: t
  which-function-mode: t
  url-handler-mode: t
  desktop-save-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.


-- 
Sam Steingold (http://sds.podval.org/) on darwin Ns 10.3.2113
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