ox-icalendar: Ignore footnotes

* lisp/ox-icalendar.el (icalendar): Ignore footnotes.

lisp/ox-icalendar.el

@@ -257,10 +257,13 @@ re-read the iCalendar file.")
 
 (org-export-define-derived-backend 'icalendar 'ascii
   :translate-alist '((clock . ignore)
+		     (footnote-definition . ignore)
+		     (footnote-reference . ignore)
 		     (headline . org-icalendar-entry)
 		     (inlinetask . ignore)
 		     (planning . ignore)
 		     (section . ignore)
+		     (inner-template . (lambda (c i) c))
 		     (template . org-icalendar-template))
   :options-alist
   '((:exclude-tags