Sometimes the $page global is set but it's just an integer, like 1, not an object which we should try to address and put in the cache. The page would work but we'd do spurious wp_cache_add

git-svn-id: http://svn.automattic.com/wordpress/trunk@6120 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/post.php

@@ -974,7 +974,7 @@ function &get_page(&$page, $output = OBJECT) {
 	global $wpdb, $blog_id;
 
 	if ( empty($page) ) {
-		if ( isset($GLOBALS['page']) ) {
+		if ( isset( $GLOBALS['page'] ) && isset( $GLOBALS['page']->ID ) ) {
 			$_page = & $GLOBALS['page'];
 			wp_cache_add($_page->ID, $_page, 'pages');
 		} else {