START SLAVE ,,,,,, is accepted as valid syntax

MariaDB [test]> START SLAVE ,,,,,,;

Query OK, 0 rows affected, 1 warning (0.000 sec)

slave_thread_opt_list:

          slave_thread_opt

	| slave_thread_opt_list ',' slave_thread_opt

	;

slave_thread_opt:

          /*empty*/ {}

        | SQL_THREAD   { Lex->slave_thd_opt|=SLAVE_SQL; }

        | RELAY_THREAD { Lex->slave_thd_opt|=SLAVE_IO; }

        ;