recent change in gnus-rescale-image broke html display in tty

[Filipp Gunbin]

Hi, this recent commit broke html article display on tty with (setq
mm-text-html-renderer 'gnus-w3m):

* 524a8eb730..: Lars Ingebrigtsen 2019-09-25 Make gnus-rescale-image
  work on modern Emacs versions

Debugger entered--Lisp error: (error "Window system frame should be used")
  image-size((image :type png :data "..." :scale 1) t)
  gnus-rescale-image((image :type png :data "..." :scale 1) (127 . 25))
  gnus-html-wash-images()
  gnus-html-wash-tags()
  gnus-article-html((#<buffer  *mm*-711294> ("text/html" (charset . "utf-8")) 
quoted-printable nil nil nil nil nil))
  mm-inline-text-html((#<buffer  *mm*-711294> ("text/html" (charset . "utf-8")) 
quoted-printable nil nil nil nil nil))
  mm-display-inline((#<buffer  *mm*-711294> ("text/html" (charset . "utf-8")) 
quoted-printable nil nil nil nil nil))
  mm-display-part((#<buffer  *mm*-711294> ("text/html" (charset . "utf-8")) 
quoted-printable nil nil nil nil nil) t)
  gnus-mime-display-single((#<buffer  *mm*-711294> ("text/html" (charset . 
"utf-8")) quoted-printable nil nil nil nil nil))
  gnus-mime-display-part((#<buffer  *mm*-711294> ("text/html" (charset . 
"utf-8")) quoted-printable nil nil nil nil nil))
  ...

Thanks,
Filipp