fix sql error as reported by a Romanian anon

inc/functions.php

@@ -2047,7 +2047,8 @@ function buildThread50($id, $return = false, $mod = false, $thread = null, $anti
 
 
 		if ($query->rowCount() == $config['noko50_count']+1) {
-			$count = prepare(sprintf("SELECT COUNT(`id`) as `num` FROM ``posts_%s`` WHERE `thread` = :thread UNION ALL SELECT COUNT(`id`) FROM ``posts_%s`` WHERE `file` IS NOT NULL AND `thread` = :thread", $board['uri'], $board['uri']));
+			$count = prepare(sprintf("SELECT COUNT(`id`) as `num` FROM ``posts_%s`` WHERE `thread` = :thread UNION ALL
+						  SELECT SUM(`num_files`) FROM ``posts_%s`` WHERE `files` IS NOT NULL AND `thread` = :thread", $board['uri'], $board['uri']));
 			$count->bindValue(':thread', $id, PDO::PARAM_INT);
 			$count->execute() or error(db_error($count));