bug#53489: 28.0.91; multi-frame images cannot be navigated in image-mode

[YAMAMOTO Mitsuharu]

Steps to reproduce:

1. Save the attached TIFF file as attach.tiff.
2. $ emacs -Q attach.tiff &
3. Notice that the image contains multiple frames.
4. Type `f' (image-next-frame).

Expected behavior:
Switch to the next frame.  Emacs 27 works as expected.

Actual behavior:
Wrong type argument: number-or-marker-p, nil

This seems to be a regression introduced by the following change:

commit 4aa4a8f9525efa6453816aa588ad178b01df554d
Author: Lars Ingebrigtsen <larsi@gnus.org>
Date:   Mon May 3 11:45:22 2021 +0200

    Speed up animation of non-displayed images
    
    * lisp/image.el (image-animate): Only compute the animation data
    once -- this avoids recomputing the image on every iteration when
    the image is not displayed (bug#47895).

                                     YAMAMOTO Mitsuharu
                                mituharu@math.s.chiba-u.ac.jp

In GNU Emacs 28.0.91 (build 2, x86_64-apple-darwin20.6.0, GTK+ Version 3.24.31, 
cairo version 1.17.4)
 of 2022-01-24 built on YAMAMOTO-no-iMac-5K.local
Repository revision: 6d3608be88e1b30d2d10ee81f14dd485275c20ff
Repository branch: emacs-28
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description:  macOS 11.6.2

Configured using:
 'configure --without-ns --with-modules LDFLAGS=-L/opt/local/lib
 CPPFLAGS=-I/opt/local/include'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBXML2 MODULES NOTIFY KQUEUE PDUMPER PNG RSVG THREADS TIFF
TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM GTK3 ZLIB