SQL & PL/SQL

I am getting the following error in one sequence and other one
in another sequence.

ORA-06550: line 5, column 13: PLS-00316: PL/SQL TABLEs must
currently use a single binary_integer index.

The following is my code

create or replace type TKG as object (
xx1 varchar2(10),
xx2 varchar2(10)
) ;
/
create or replace type TKGVARRAY as varray(150) of TKG ;
/
create or replace type TKGTABLE is table of TKG ;
/

Calling program is
---------------------
1 declare
2 tkgarray TKGVARRAY ;

3 begin
4 tkgarray := tkgarray( TKG('xx1', 'xx3'), TKG('xx1', 'xx3'));

5 /*tkgarray.extend ;
6 tkgarray(1) := tkg('xx1', 'xx3') ;
7 tkgarray.extend ;
8 tkgarray(2) := tkg('xx2', 'xx4') ;
9 */
10 sddr_cir_stp_i(tkgarray) ;

11 commit ;

12 end ;

When I comment the line 4 and uncomment the line 5 to 9, then I
am getting the following error

ORA-06531: Reference to uninitialized collection.

Please somebody help me. The same code was working in my
previous project but not working in the current project.