RS concurrent modification in administration > invalidate sessions

<dispatchinfo>
	<componentinfo>
		<compname>ffo_main_null</compname>
		<compclass>org.olat.core.gui.components.form.flexible.impl.FormWrapperContainer</compclass>
		<extendedinfo>n/a</extendedinfo>
		<event>
			<class&gt;org.olat.core.gui.components.form.flexible.impl.FormEvent</class&gt;
			<command>done</command>
			<tostring>com:done,org.olat.core.gui.components.form.flexible.impl.FormEvent@2f23a1</tostring>
		</event>
	</componentinfo>
	<controllerinfo>
		<controllername>org.olat.admin.sysinfo.UserSessionConfigAdminController</controllername>
		<controllername>org.olat.admin.sysinfo.UserSessionAdminController</controllername>
		<controllername>org.olat.admin.SystemAdminMainController</controllername>
		<controllername>org.olat.core.commons.fullWebApp.BaseFullWebappController</controllername>
	</controllerinfo>
</dispatchinfo>

Throwable: java.util.ConcurrentModificationException
message:null,java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1437)
at java.util.HashMap$KeyIterator.next(HashMap.java:1461)
at java.util.AbstractCollection.addAll(AbstractCollection.java:343)
at java.util.TreeSet.addAll(TreeSet.java:312)
at org.olat.core.util.session.UserSessionManager.invalidateOldestSessions(UserSessionManager.java:577)
at org.olat.admin.sysinfo.UserSessionConfigAdminController.formInnerEvent(UserSessionConfigAdminController.java:158)
at org.olat.core.gui.components.form.flexible.impl.FormBasicController.event(FormBasicController.java:408)
at org.olat.core.gui.control.DefaultController.dispatchEvent(DefaultController.java:202)
at org.olat.core.gui.components.AbstractComponent$1.run(AbstractComponent.java:240)
at org.olat.core.logging.activity.ThreadLocalUserActivityLoggerInstaller.runWithUserActivityLogger(ThreadLocalUserActivityLoggerInstaller.java:108)