avoid log(0) error with nullif

[oracle@stormking cdb12102 SQL]$ cat log0.SQL
SELECT p, log ( 10,  NULLIF ( p, 0 ) ) lp
FROM
(
        SELECT POWER ( 10, level - 3 ) p
        FROM dual
        CONNECT BY level <= 5
        UNION
        SELECT 0
        FROM dual
)
ORDER BY p
;

quit
[oracle@stormking cdb12102 SQL]$ sqlplus u/u@//stormking:1521/pdbm @ log0.SQL

SQL*Plus: Release 12.1.0.2.0 Production ON Fri Oct 23 23:02:56 2015

Copyright (c) 1982, 2014, Oracle.  ALL rights reserved.

LAST Successful login TIME: Fri Oct 23 2015 23:02:27 -04:00

Connected TO:
Oracle DATABASE 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
WITH the Partitioning, Automatic Storage Management, OLAP, Advanced Analytics
AND REAL Application Testing options


         P         LP
---------- ----------
         0
       .01         -2
        .1         -1
         1          0
        10          1
       100          2

6 ROWS selected.