USNChangedMapper throws NPEs if AD does not return the uSNChanged attribute

2011-11-25 09:50:16,614 pool-20-thread-1 WARN ServiceRunner     [directory.ldap.mapper.UserContextMapper] Failed to map attribute <uSNChanged> from context with DN <cn=Delete ME. User,ou=scratch,dc=ad,dc=atlassian,dc=com>
java.lang.NullPointerException
	at com.atlassian.crowd.directory.ldap.mapper.attribute.USNChangedMapper.getValues(USNChangedMapper.java:28)
	at com.atlassian.crowd.directory.ldap.mapper.UserContextMapper.mapFromContext(UserContextMapper.java:57)
	at org.springframework.ldap.core.ContextMapperCallbackHandler.getObjectFromNameClassPair(ContextMapperCallbackHandler.java:67)
	at org.springframework.ldap.core.CollectingNameClassPairCallbackHandler.handleNameClassPair(CollectingNameClassPairCallbackHandler.java:50)
	at org.springframework.ldap.core.LdapTemplate.search(LdapTemplate.java:297)
	at org.springframework.ldap.core.LdapTemplate.search(LdapTemplate.java:237)
	at com.atlassian.crowd.directory.SpringLDAPConnector.pageSearchResults(SpringLDAPConnector.java:300)
	at com.atlassian.crowd.directory.SpringLDAPConnector.searchEntitiesWithRequestControls(SpringLDAPConnector.java:366)
	at com.atlassian.crowd.directory.SpringLDAPConnector.searchEntities(SpringLDAPConnector.java:351)
	at com.atlassian.crowd.directory.SpringLDAPConnector.searchUserObjects(SpringLDAPConnector.java:541)
	at com.atlassian.crowd.directory.SpringLDAPConnector.searchUsers(SpringLDAPConnector.java:910)
	at com.atlassian.crowd.directory.ldap.cache.UsnChangedCacheRefresher$1.call(UsnChangedCacheRefresher.java:181)
	at com.atlassian.crowd.directory.ldap.cache.UsnChangedCacheRefresher$1.call(UsnChangedCacheRefresher.java:176)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:680)
2011-11-25 09:50:16,615 pool-20-thread-1 INFO ServiceRunner     [directory.ldap.cache.UsnChangedCacheRefresher] found [ 2 ] remote users in [ 20ms ]