GRANT PROXY with empty password incorrectly checks grantor's privileges

CREATE USER u1@localhost;

CREATE USER u2@localhost IDENTIFIED BY 'oldpassword';

GRANT ALL PRIVILEGES ON *.* TO u2@localhost WITH GRANT OPTION;

show create user u2@localhost;

connect u,localhost,u1;

SHOW GRANTS;

GRANT PROXY ON u1@localhost TO u2@localhost IDENTIFIED VIA

  '' OR mysql_native_password USING PASSWORD('newpassword');

connection default;

show create user u2@localhost;

drop user u1@localhost;

drop user u2@localhost;