SQL & PL/SQL

I have following piece of sample code, and got 'ORA-30732 table contains no user-visible columns' when I run it, can anyone help me to figure out what the problem is?
( following is just a testing code to validate something, the logic makes no sense here.)

CREATE OR REPLACE TYPE Old_New_Obj AS OBJECT (Old_Id int, New_Id int);
/
CREATE OR REPLACE TYPE Old_New_TB AS TABLE OF Old_New_Obj;
/
Create table ttt(old_id int, new_id int);
/
declare
result int;
tb Old_New_TB;
tb1 Old_New_TB;

begin
select Old_New_Obj(1,2)
bulk collect into tb
from dual;


select Old_New_Obj(1,4)
bulk collect into tb1
from dual;

insert into ttt (new_id )
select b.new_id
from table(tb) a inner join table(tb1) b on a.old_id = b.old_id
where rownum = 1;

select new_id into result from ttt where rownum =1;

dbms_output.put_line(result);
end;