Index: modules/node/node.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/node/node.module,v
retrieving revision 1.776.2.32
diff -u -p -r1.776.2.32 node.module
--- modules/node/node.module	26 Dec 2008 22:25:40 -0000	1.776.2.32
+++ modules/node/node.module	14 Jan 2009 02:38:00 -0000
@@ -2753,6 +2753,11 @@ function node_search_validate($form_id, 
 function node_access($op, $node = NULL) {
   global $user;
 
+  if (!$node || !in_array($op, array('view', 'update', 'delete', 'create'), TRUE)) {
+    // If there was no node to check against, or the $op was not one of the
+    // supported ones, we return access denied.
+    return FALSE;
+  }
   // Convert the node to an object if necessary:
   if ($op != 'create') {
     $node = (object)$node;