Error in instant messaging session counter due to unsynchronized code block

2012-09-16 04:42:30,819 [schedulerFactoryBean_Worker-2] ERROR CountSessionsOnServerJob - OLAT::ERROR ^% N14-E65 ^% org.olat.instantMessaging ^% n/a ^% n/a ^% n/a ^% n/a ^% Cannot count the users online ^%
>>>stack of 1.cause::java.util.ConcurrentModificationException: null
-> at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$EntryIterator.next(HashMap.java:834)
at java.util.HashMap$EntryIterator.next(HashMap.java:832)
at java.util.HashMap.putAllForCreate(HashMap.java:435)
at java.util.HashMap.(HashMap.java:225)
at org.olat.instantMessaging.ClientManagerImpl.getClients(ClientManagerImpl.java:313)
at org.olat.instantMessaging.syncservice.SessionCountLocal.countSessions(SessionCountLocal.java:47)
at org.olat.instantMessaging.CountSessionsOnServerJob.executeWithDB(CountSessionsOnServerJob.java:41)
at org.olat.core.commons.scheduler.JobWithDB.executeInternal(JobWithDB.java:61)
at org.springframework.scheduling.quartz.QuartzJobBean.execute(Qua[...]

Synchronized the clients map in ClientManagerImpl to fix the problem