NPE in change log temp processor when adding group set if parent doesn't exist

This could happen if change log entries are out of order.

Or if upgrading from a pre-2.6.17 release where (for example) a container not upgraded yet creates a group and the group is deleted before pit sync runs.
Caused by: java.lang.NullPointerException: Problem in HibernateSession: HibernateSession (202d83b9): new, notReadonly, READ_WRITE_NEW, notActiveTransaction, session (1ac32da1),
jobName: CHANGE_LOG_changeLogTempToChangeLog
at edu.internet2.middleware.grouper.changeLog.ChangeLogTempToEntity.processGroupSetAdd(ChangeLogTempToEntity.java:1967)