Subject: 27.0.50; Regression in image type auto-detection

From: Juri Linkov <[email-masked]>
Date: Tue, 09 Oct 2018 01:08:13 +0300

Tags: patch

A recent change in image-mode.el broke a useful feature that
automatically detects an image type, so now visiting an image file
without a file extension signals the error "upcase(nil) -
(wrong-type-argument char-or-string-p nil)".  This patch fixes it:

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index 19fa28d440..eb7b410f4a 100644
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -781,8 +785,9 @@ image-toggle-display-image
 (defun image--imagemagick-wanted-p (filename)
   (and (fboundp 'imagemagick-types)
        (not (eq imagemagick-types-inhibit t))
-       (not (memq (intern (upcase (file-name-extension filename)) obarray)
-                  imagemagick-types-inhibit))))
+       (not (and (file-name-extension filename)
+                 (memq (intern (upcase (file-name-extension filename)) obarray)
+                       imagemagick-types-inhibit)))))
 
 (defun image-toggle-hex-display ()
   "Toggle between image and hex display."