Load org-icalendar when exporting agenda file to ics

lisp/ChangeLog

@@ -1,5 +1,8 @@
 2009-06-27  Carsten Dominik  <carsten.dominik@gmail.com>
 
+	* org-agenda.el (org-write-agenda): Make sure org-icalendar is
+	loaded.
+
 	* org.el (org-map-entries): No longer force
 	`org-tags-match-list-sublevels' to t during a todo-only tags
 	search.

lisp/org-agenda.el

@@ -2157,6 +2157,7 @@ higher priority settings."
 			     (expand-file-name file))
 	       (message "PDF written to %s" file))
 	      ((string-match "\\.ics\\'" file)
+	       (require 'org-icalendar)
 	       (let ((org-agenda-marker-table
 		      (org-create-marker-find-array
 		       (org-agenda-collect-markers)))