org-flag-drawer: display the position where the error occurs.

Patch by Friedrich Delgado Friedrichs <friedel@nomaden.org>.

lisp/ChangeLog

@@ -1,3 +1,7 @@
+2009-08-19  Friedrich Delgado Friedrichs <friedel@nomaden.org>  (tiny change)
+
+	* org.el (org-flag-drawer): More useful error.
+
 2009-08-19  Carsten Dominik  <carsten.dominik@gmail.com>
 
 	* org-remember.el (org-remember-apply-template): Use

lisp/org.el

@@ -5291,7 +5291,7 @@ are at least `org-cycle-separator-lines' empty lines before the headline."
 	     "^[ \t]*:END:"
 	     (save-excursion (outline-next-heading) (point)) t)
 	    (outline-flag-region b (point-at-eol) flag)
-	  (error ":END: line missing"))))))
+	  (error ":END: line missing at position %s" b))))))
 
 (defun org-subtree-end-visible-p ()
   "Is the end of the current subtree visible?"