Index: widgets.php
===================================================================
--- widgets.php	(revision 8534)
+++ widgets.php	(working copy)
@@ -57,7 +57,7 @@
 		'after_title' => "</h2>\n",
 	);
 
-	$sidebar = array_merge($defaults, $args);
+	$sidebar = array_merge($defaults, (array) $args);
 
 	$wp_registered_sidebars[$sidebar['id']] = $sidebar;