bug#34981: 27.0.50; gnus-group-select-group errors with wrong type argument

[Alex Branham]

I'm trying to start using gnus and perhaps ran into a bug. I'm trying to
view the emacs-devel mailing list through gnus, for starters.

>From emacs -q, built from the latest git master (commit
03e916beb0186f3707cd238650298870bf471575):

(setq gnus-select-method
      '(nntp "gnus.user" (nntp-address "news.gmane.org")))

M-x gnus

A A (gnus-group-list-active)

C-s emacs.devel C-s

RET (gnus-group-select-group)

produces:

Debugger entered--Lisp error: (wrong-type-argument symbolp (827 . 234690))
  symbol-name((827 . 234690))
  gnus-group-group-name()
  redisplay_internal\ \(C\ function\)()
  redisplay()
  sit-for(2)
  execute-extended-command(nil "toggle-debug-on-error" "toggle-debug-on-error")
  funcall-interactively(execute-extended-command nil "toggle-debug-on-error" 
"toggle-debug-on-error")
  call-interactively(execute-extended-command nil nil)
  command-execute(execute-extended-command)


In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.5)
 of 2019-03-24 built on localhost
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: NixOS 18.09.2375.680f9d7ea90 (Jellyfish)

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND DBUS GSETTINGS GLIB NOTIFY INOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS LIBSYSTEMD JSON
PDUMPER GMP

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix