How to handle multiple audited objects?

We have extended NmsAuditAPI to audit the clearing of alerts by an operator. The audit() method gets invoked for all the operator actions.

We are seeing the following exception, when clearing multiple alerts at the same time -
nested exception is:
java.lang.NullPointerException,
Cause:
java.lang.NullPointerException
at com.adventnet.security.authorization.AuthorizationEngineExtImpl.audit(AuthorizationEngineExtImpl.java:476)
at com.adventnet.security.authorization.AuthorizationEngineExtImpl.isAuthorized(AuthorizationEngineExtImpl.java:141)
at com.adventnet.nms.util.NmsUtil.checkAuthorization(NmsUtil.java:2702)
at com.adventnet.nms.startnms.MainSocketSessionBE.checkAuthorization(MainSocketSessionBE.java:1035)
at com.adventnet.nms.alertdb.AlertSessionBE.checkAuthorization(AlertSessionBE.java:2010)
at com.adventnet.nms.alertdb.AlertSessionBE.performClearOperation(AlertSessionBE.java:1357)
at com.adventnet.nms.alertdb.AlertSessionBE.resolveAndPerformAction(AlertSessionBE.java:1592)
at com.adventnet.nms.alertdb.AlertSessionBE.receiveTheData(AlertSessionBE.java:908)
at com.adventnet.nms.alertdb.AlertSessionBE.receive(AlertSessionBE.java:146)
at com.adventnet.nms.alertdb.AlertSessionBE.receive(AlertSessionBE.java:115)

How does the 'auditedObj' property in the 'auditProperties' parameter to the audit() method, get handled in this case?

Thanks.