SQL> create table test (id number, salary number);

Table created.

SQL> insert all
  2    into test values (1, 100)
  3    into test values (2, null)
  4    into test values (3, 300)
  5  select * from dual;

3 rows created.

SQL> -- this might be your current situation:
SQL> select id, salary from test order by id;

        ID     SALARY
---------- ----------
         1        100
         2
         3        300

SQL> -- this might be your improved query:
SQL> select id, nvl(salary, 0) salary from test order by id;

        ID     SALARY
---------- ----------
         1        100
         2          0
         3        300

select name into l_name
  from some_table 
  where id = <non-existent id from your matrix report>;

select MAX(name) into ...