PL SQL trigger to restrict employee in department

i am making a trigger in plsql to restrict the employees after reaching define limit  but it give me error - ORA-01403: no data found on my form.anyone help

create or replace trigger DEPT_STRENTH

  before insert or update on empmasterinfo

  for each row

DECLARE

  -- local variables here

  EMP_Count    NUMBER;

  MAX_Strength NUMBER;

BEGIN

  select d.strength

    into MAX_Strength

    from dept_strength d

   where d.Mainid = :new.Mainid

     and d.orgelementname = :new.orgelementname;

  select count(e.employeeid)

    into EMP_Count

    from empmasterinfo e

   where e.emp_status = 0

     and e.Mainid = :new.mainid

     and e.orgelementname = :new.orgelementname;

  if MAX_Strength <= EMP_Count then

  

    RAISE_APPLICATION_ERROR(-20101,

                            'Maximum Number of Employees in Department Reached');

  else

    null;

  end if;

end DEPT_STRENTH;