Coverity #1394567: null pointer dereference

** CID 1394567:  Null pointer dereferences  (FORWARD_NULL)

/src/log/log.c: 1908 in __log_has_hole()

*** CID 1394567:  Null pointer dereferences  (FORWARD_NULL)

/src/log/log.c: 1908 in __log_has_hole()

1902                            /*

1903                             * Find where the next log record starts after the

1904                             * hole.

1905                             */

1906                            for (p = buf, buf_left = rdlen; buf_left > 0;

1907                                 buf_left -= rdlen, p += rdlen) {

>>>     CID 1394567:  Null pointer dereferences  (FORWARD_NULL)

>>>     Dereferencing null pointer "log".

1908                                    rdlen = WT_MIN(log->allocsize, buf_left);

1909                                    if (memcmp(p, zerobuf, rdlen) != 0)

1910                                            break;

1911                            }

1912                            /*

1913                             * A presumed log record begins here where the buffer

/*

 * It can be very slow looking for the last real record in the log

 * in very small chunks.  Walk a megabyte at a time.  If we find a

 * part of the log that is not just zeroes we know this log file

 * has a hole in it.

 */

buf = zerobuf = NULL;

if (log == NULL || log->allocsize < WT_MEGABYTE)

        bufsz = WT_MEGABYTE;

else

        bufsz = log->allocsize;