Error in estimation of space

@

I'm trying to make a PL/SQL script that will calculate the estimated space for 1000000 rows within a schema but the .SQL script error out with this error. Could you please tell / fix the error?

SQL> @  estm_tab_size_input
Enter value for table_name: TRIP_SUMMARY
old  11: where table_name=upper('&TABLE_NAME')
new  11: where table_name=upper('TRIP_SUMMARY')
DECLARE
*
ERROR at line 1:
ORA-06531: Reference to uninitialized collection
ORA-06512: at "SYS.DBMS_SPACE", line 2661
ORA-06512: at line 33

DECLARE
 ub NUMBER;
 ab NUMBER;
 v_v1 varchar2(200) := 'sys.create_table_cost_columns( ';
 v_v2 varchar2(200) := NULL ;
 v_all varchar2(1000) := NULL;