How to replace empty, multi-column result with single 'none'

If it is possible to make query in Oracle which will return single column/row with value “none” instead of empty, multi-column result?
Otherwise return proper amount of columns with result.
This is example query in my Oracle DB which returns empty result.

SELECT *
  FROM (select '- Tablespace ->',
               t.tablespace_name ktablespace,
               '- Type->',
               substr(t.contents, 1, 1) tipo,
               '- Used(MB)->',
               trunc((d.tbs_size - nvl(s.free_space, 0)) / 1024 / 1024) ktbs_em_uso,
               '- ActualSize(MB)->',
               trunc(d.tbs_size / 1024 / 1024) ktbs_size,
               '- MaxSize(MB)->',
               trunc(d.tbs_maxsize / 1024 / 1024) ktbs_maxsize,
               '- FreeSpace(MB)->',
               trunc(nvl(s.free_space, 0) / 1024 / 1024) kfree_space,
               '- Space->',
               trunc((d.tbs_maxsize - d.tbs_size + nvl(s.free_space, 0)) / 1024 / 1024) kspace,
               '- Perc->',
               decode(d.tbs_maxsize,
                      0,
                      0,
                      trunc((d.tbs_size - nvl(s.free_space, 0)) * 100 /
                            d.tbs_maxsize)) kperc
          from (select SUM(bytes) tbs_size,
                       SUM(decode(sign(maxbytes - bytes), -1, bytes, maxbytes)) tbs_maxsize,
                       tablespace_name tablespace
                  from (select nvl(bytes, 0) bytes,
                               nvl(maxbytes, 0) maxbytes,
                               tablespace_name
                          from dba_data_files
                        union all
                        select nvl(bytes, 0) bytes,
                               nvl(maxbytes, 0) maxbytes,
                               tablespace_name
                          from dba_temp_files)
                 group by tablespace_name) d,
               (select SUM(bytes) free_space, tablespace_name tablespace
                  from dba_free_space
                 group by tablespace_name) s,
               dba_tablespaces t
         where t.tablespace_name = d.tablespace(+)
           and t.tablespace_name = s.tablespace(+)
         order by 8)
 where kperc > 98
   and tipo <> 'T'
   and tipo <> 'U'

But application I’m using this select in waits result or “none”, but not empty result.
I have tried to figure out this problem with CASE, COALESCE statement but nothing worked out.