Problems Formatting String with Spaces in BI Publisher

Case:

I have a report that concatenates multiple columns into multiple rows.  i.e.

Begin

    Select rpad('ABC1',4) || ' ' || rpad('ABC2',4)||chr(10) into X1 from dual;

   Select rpad('ABC3',4) || ' ' || rpad('ABC4',4)||chr(10) into X2 from dual;

   Select rpad('ABC5',4) || ' ' || rpad('ABC6',4)||chr(10) into X3 from dual;

   String1 := X1||X2||X3; -- concat all values into one string

End;

Expected Results (String1):

  ABC1 ABC2

  ABC3 ABC4

  ABC5 ABC6

Notice that the values are lined up correctly.

 

Problem Case

If 'ABC3' was null ('    ') then the correct results for