call by reference

[shahnehav]

select * from table(cast(max_salary_dept(cursor(select * from departments),cursor(select d.department_name , max(e.salary) from employees e , departments d where e.department_id = d.department_id group by d.department_name) )as output_tbl))


When i Execute the above query i get following error :

ERROR at line 1:
ORA-06531: Reference to uninitialized collection
ORA-06512: at "HR.MAX_SALARY_DEPT", line 29

Kinldy,
Resolve this error