org.el: don't escape image links with no description.

(org-make-link-string): Don't escape image links when no description
is provided by the user.  Otherwise those images won't be recognized
as images when trying to display inline pictures.

lisp/org.el

@@ -8686,16 +8686,19 @@ according to FMT (default from `org-email-link-description-format')."
       (setq description (replace-match "{" t t description)))
     (while (string-match "\\]" description)
       (setq description (replace-match "}" t t description))))
-  (when (equal (org-link-escape link) description)
+  (when (equal link description)
     ;; No description needed, it is identical
     (setq description nil))
   (when (and (not description)
+	     (not (string-match (org-image-file-name-regexp) link))
 	     (not (equal link (org-link-escape link))))
     (setq description (org-extract-attributes link)))
-  (setq link (if (string-match org-link-types-re link)
-		 (concat (match-string 1 link)
-			 (org-link-escape (substring link (match-end 1))))
-	       (org-link-escape link)))
+  (setq link
+	(cond ((string-match (org-image-file-name-regexp) link) link)
+	      ((string-match org-link-types-re link)
+	       (concat (match-string 1 link)
+		       (org-link-escape (substring link (match-end 1)))))
+	      (t (org-link-escape link))))
   (concat "[[" link "]"
 	  (if description (concat "[" description "]") "")
 	  "]"))