Problem:
========

null_audit_event_record variable is not intended to be modified outside
of the null_audit plugin. null_audit_event_record buffer must be allocated/deallocated
from within a plugin.

Fix:
====

null_audit_event_record is read only variable.

Reviewed-by:
============

Arun Kuruvila <arun.kuruvila@oracle.com>
Georgi Kodinov <georgi.kodinov@oracle.com>