transport-next-link: Keep original description when on whitespace

A to-be-transported link is allowed to have a description if a new
description isn't specified by the word at point or the selected text.
In this case, don't drop the original description during transport.

org-link-edit.el

@@ -381,9 +381,10 @@ END."
       (delete-region link-beg link-end)
       (insert (org-make-link-string
                link
-               (and desc-bounds
-                    (delete-and-extract-region (car desc-bounds)
-                                               (cdr desc-bounds))))))))
+               (if desc-bounds
+                   (delete-and-extract-region (car desc-bounds)
+                                              (cdr desc-bounds))
+                 orig-desc))))))
 
 (provide 'org-link-edit)
 ;;; org-link-edit.el ends here

test-org-link-edit.el

@@ -552,6 +552,14 @@ website"
                 "Here is<point> Org's website http://orgmode.org/"
               (org-link-edit-transport-next-link)
               (buffer-string))))
+  ;; Transported links are allow to have an existing description when
+  ;; point is on whitespace.
+  (should
+   (string= "Here is\[\[http://orgmode.org/\]\[descrption\]\] Org's website "
+            (org-test-with-temp-text
+                "Here is<point> Org's website \[\[http://orgmode.org/\]\[descrption\]\]"
+              (org-link-edit-transport-next-link)
+              (buffer-string))))
   ;; Fail if point is on a link.
   (should-error
    (org-test-with-temp-text