3418395 - Errors in default traces related to Forums

There are a lot of errors in Portal's developer log related to Forum:

EXAMPLE :
java.lang.NullPointerException: while trying to invoke the method com.sap.netweaver.coll.forums.cluster.locking.Lock.isLocked() of a null object loaded from field com.sap.netweaver.coll.forums.cluster.tasks.TaskService.lock of an object loaded from local variable 'this'
at com.sap.netweaver.coll.forums.cluster.tasks.TaskService.isSenior(TaskService.java:64)
at com.jivesoftware.forum.watches.WatchSettingsManagerImpl.queryForUsers(WatchSettingsManagerImpl.java:121)
at com.jivesoftware.forum.watches.WatchSettingsManagerImpl.emailUsersWhoNeedBatchEmails(WatchSettingsManagerImpl.java:114)
at com.jivesoftware.forum.watches.WatchSettingsManagerImpl$1.run(WatchSettingsManagerImpl.java:51)
at com.jivesoftware.util.TaskEngine$GuardedRunnable.run(TaskEngine.java:427)
at com.jivesoftware.util.TaskEngine$TaskEngineWorker.run(TaskEngine.java:355)

Netweaver portal 7.5 

com.sap.netweaver.coll.forums.cluster.locking.Lock.isLocked() of a null object loaded from field, TaskService.lock of an object loaded from local variable 'this', forum. wiki , KBA , BC-COM-FOR , Forums , Problem