* lisp/image/image-dired-util.el
(image-dired--with-dired-buffer): New macro.
* lisp/image/image-dired.el (image-dired-track-original-file)
(image-dired--on-file-in-dired-buffer)
(image-dired--do-mark-command)
(image-dired--on-file-in-dired-buffer)
(image-dired-jump-original-dired-buffer)
(image-dired-thumb-file-marked-p, image-dired-delete-marked):
Use above new macro to simplify and improve error handling.
(image-dired-show-all-from-dir): Simplify removing Dired marks.
(image-dired-thumb-update-marks): Avoid triggering above new error
handling.