bug#32633: 26.1; delete-trailing-whitespace hangs on image buffer

[Pierre Neidhardt <mail@ambrevar.xyz>]

Recipe:

- emacs -Q /path/to/image.png
- M-x delete-trailing-whitespace

=> hangs forever.

The issue was mentioned in

	https://github.com/walseb/blimp/issues/2
  
In GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-07-19 built on localhost
Windowing system distributor 'The X.Org Foundation', version 11.0.12000000
Recent messages:
Copied https://melpa.org/#/whitespace-cleanup-mode
Invalid face reference: nil [30 times]
Quit [2 times]
QuitInvalid face reference: nil
Invalid face reference: nil [2 times]
[mu4e] Found 11 matching messages
[mu4e] Found 3 matching messages
Mark set
[mu4e] Found 24 matching messages
[mu4e] Found 1 matching message

Configured using:
 'configure
 CONFIG_SHELL=/gnu/store/rbrandv7anzjxqkr40d7fkanzssslk4b-bash-minimal-4.4.19/bin/bash
 SHELL=/gnu/store/rbrandv7anzjxqkr40d7fkanzssslk4b-bash-minimal-4.4.19/bin/bash
 --prefix=/gnu/store/q01qp6ypjhdl37wnpj6ff6f8dn90pzjf-emacs-26.1
 --enable-fast-install'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GSETTINGS NOTIFY ACL
GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS
GTK3 X11 THREADS

Important settings:
  value of $LANG: en_US.utf8
  locale-coding-system: utf-8-unix

Major mode: mu4e-headers

Minor modes in effect:
  recentf-mode: t
  global-magit-file-mode: t
  magit-auto-revert-mode: t
  global-git-commit-mode: t
  global-fish-completion-mode: t
  fish-completion-mode: t
  global-mu4e-conversation-mode: t
  mu4e-conversation-mode: t
  hl-line-mode: t
  global-semanticdb-minor-mode: t
  global-semantic-idle-scheduler-mode: t
  yas-global-mode: t
  yas-minor-mode: t
  pdf-occur-global-minor-mode: t
  semantic-mode: t
  global-hl-todo-mode: t
  helm-top-poll-mode: t
  dired-async-mode: t
  helm-mode: t
  diff-auto-refine-mode: t
  helm-descbinds-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  async-bytecomp-package-mode: t
  shell-dirtrack-mode: t
  evil-mode: t
  evil-local-mode: t
  engine-mode: t
  desktop-save-mode: t
  show-paren-mode: t
  savehist-mode: t
  save-place-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  window-divider-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  size-indication-mode: t
  line-number-mode: t
  transient-mark-mode: t

<#secure method=pgpmime mode=sign>

-- 
Pierre Neidhardt
https://ambrevar.xyz/