Sun Mar  1 03:04:19 2009  Akinori MUSHA  <knu@iDaemons.org>

	* class.c (rb_singleton_class_clone): Qnil must be used for a null
	  class reference when we use NIL_P() to check class reference
	  validity.  The bug was exposed by the spec test of Sequel.

	* eval.c (ruby_init): Use NEW_CREF().

Index: ruby_1_8/class.c
===================================================================
--- ruby_1_8/class.c	(revision 22678)
+++ ruby_1_8/class.c	(revision 22679)
@@ -153,7 +153,7 @@
 		data.klass = obj;
 		break;
 	      default:
-		data.klass = 0;
+		data.klass = Qnil;
 		break;
 	    }