replicate_rewrite_db does not work for single char database name

# TBF - difference in row level logging

-- source include/have_binlog_format_mixed_or_statement.inc

-- source include/master-slave.inc

connection master;

SET sql_log_bin= 0;

create database x;

SET sql_log_bin= 1;

use x;

connection slave;

SET sql_log_bin= 0;

create database y;

SET sql_log_bin= 1;

use y;

--connection master

create table t1(a int);

insert into t1 values(1);

--sync_slave_with_master

select * from y.t1;

--source include/rpl_end.inc

"--replicate-rewrite-db=x->y"

CURRENT_TEST: rpl.rpl_one_char_db_rewrt_db

180902 19:14:02 [ERROR] Bad syntax in replicate-rewrite-db - empty FROM db!

180902 19:14:02 [ERROR] Aborting