Fix elmo-set-auto-coding fails without optional argument

elmo-util.el.diff

diff --git a/elmo/elmo-util.el b/elmo/elmo-util.el
index 4f2e5cfd..ed9247be 100644
--- a/elmo/elmo-util.el
+++ b/elmo/elmo-util.el
@@ -103,10 +103,11 @@ with FILENAME which defaults to `buffer-file-name'."
 	  (car (find-operation-coding-system 'insert-file-contents
 					     filename)))
     (let (auto-coding-alist)
-      (condition-case nil
+      (condition-case error
 	  (funcall (symbol-value 'set-auto-coding-function)
-		   nil (- (point-max) (point-min)))
-	(error nil)))))
+		   "" (- (point-max) (point-min)))
+	(error (message "Error in %s, %s"
+			set-auto-coding-function (cdr error)))))))
 
 (defun elmo-object-load (filename &optional mime-charset no-err)
   "Load OBJECT from the file specified by FILENAME.