Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 17114)
+++ wp-includes/post.php	(working copy)
@@ -3257,12 +3257,14 @@
 		$page = get_page($page);
 	$uri = $page->post_name;
 
-	// A page cannot be it's own parent.
+	// A page cannot be its own parent.
 	if ( $page->post_parent == $page->ID )
 		return $uri;
 
-	while ($page->post_parent != 0) {
-		$page = get_page($page->post_parent);
+	while (
+		$page->post_parent != 0 &&
+		( $page = get_page( $page->post_parent ) )
+	) {
 		$uri = $page->post_name . "/" . $uri;
 	}
 
@@ -5229,4 +5231,4 @@
 }
 add_filter( 'wp_get_object_terms', '_post_format_wp_get_object_terms' );
 
-?>
\ No newline at end of file
+?>