Apply filteres when returning empty array from get_pages. Props epper. fixes #4712 for 2.3

git-svn-id: http://svn.automattic.com/wordpress/branches/2.3@6205 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/post.php

@@ -1203,7 +1203,7 @@ function &get_pages($args = '') {
 	$pages = $wpdb->get_results($query);
 
 	if ( empty($pages) )
-		return array();
+		return apply_filters('get_pages', array(), $r);
 
 	// Update cache.
 	update_page_cache($pages);