org-src.el (org-edit-src-code): Fix bug on Emacs <24.1.

* org-src.el (org-edit-src-code): Fix bug triggered by the
sexp (copy-marker nil) on Emacs <24.1.

Thanks to Bernt Hansen for reporting this.

lisp/org-src.el

@@ -228,12 +228,11 @@ buffer."
 	 (full-info (org-babel-get-src-block-info 'light))
 	 (org-mode-p (derived-mode-p 'org-mode)) ;; derived-mode-p is reflexive
 	 (beg (make-marker))
-	 ;; Move marker with inserted text for case when src block is
-	 ;; just one empty line, i.e. beg == end.
-	 (end (copy-marker nil t))
+	 (end (make-marker))
 	 (allow-write-back-p (null code))
 	 block-nindent total-nindent ovl lang lang-f single lfmt buffer msg
 	 begline markline markcol line col transmitted-variables)
+    (set-marker-insertion-type end t)
     (if (not info)
 	nil
       (setq beg (move-marker beg (nth 0 info))