PMA_mysqlDie pulls headers, no need to do it again.

sql.php

@@ -391,11 +391,6 @@ if (isset($GLOBALS['show_as_php']) || !empty($GLOBALS['validatequery'])) {
              */
             require './' . PMA_securePath($goto);
         } else {
-            /**
-             * HTML header.
-             */
-
-            require_once './libraries/header.inc.php';
             $full_err_url = (preg_match('@^(db|tbl)_@', $err_url))
                           ? $err_url . '&show_query=1&sql_query=' . urlencode($sql_query)
                           : $err_url;