Lectures: cannot cancel lecture if no reasons defined

2019-03-21 08:23:28,833 [ajp-nio2-8092-exec-30] ERROR OLATRuntimeException - OLAT::ERROR ^%^ N92-E13 ^%^ org.olat.core.logging 

https://xyz.openolat.com/auth/RepositoryEntry/17465345/lectures/0/LectureBlock/48
Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko

**RedScreen** Index: 0, Size: 0 
<dispatchinfo>
	<componentinfo>
		<compname>ffo_main_rollcall</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.modules.lecture.ui.TeacherRollCallController</controllername>
		<controllername>org.olat.modules.lecture.ui.TeacherLecturesTableController</controllername>
		<controllername>org.olat.modules.lecture.ui.TeacherOverviewController</controllername>
		<controllername>org.olat.course.run.CourseRuntimeController</controllername>
		<controllername>org.olat.core.commons.fullWebApp.BaseFullWebappController</controllername>
	</controllerinfo>
</dispatchinfo>

>>> stack of 1.cause::org.olat.core.logging.OLATRuntimeException: Index: 0, Size: 0
-> at org.olat.core.gui.exception.ExceptionWindowController.<init>(ExceptionWindowController.java:116)
   at org.olat.core.gui.exception.MsgFactory.createMessageChiefController(MsgFactory.java:57)
   at org.olat.core.gui.exception.MsgFactory.createMessageChiefController(MsgFactory.java:46)
   at org.olat.core.gui.components.Window.dispatchRequest(Window.java:589)
   at org.olat.core.gui.components.Window.doDispatchRequest(Window.java:282)
   at org.olat.core.gui.components.AbstractComponent.dispatchRequest(AbstractComponent.java:193)
   at org.olat.dispatcher.AuthenticatedDispatcher.processValidDispatchURI(AuthenticatedDispatcher.java:273)
   at org.olat.dispatcher.AuthenticatedDispatcher.execute(AuthenticatedDispatcher.java:190)
   at org.olat.core.servlets.OpenOLATServlet.executeUserRequest(OpenOLATServlet.java:294)
   at org.olat.core.servlets.OpenOLATServlet.doPost(OpenOLATServlet.java:237)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:661)
>>> stack of 2.cause::java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
-> at java.util.ArrayList.rangeCheck(ArrayList.java:657)
   at java.util.ArrayList.get(ArrayList.java:433)
   at org.olat.modules.lecture.ui.CancelRollCallConfirmationController.initForm(CancelRollCallConfirmationController.java:102)
   at org.olat.core.gui.components.form.flexible.impl.FormBasicController.initForm(FormBasicController.java:273)
   at org.olat.modules.lecture.ui.CancelRollCallConfirmationController.<init>(CancelRollCallConfirmationController.java:67)
   at org.olat.modules.lecture.ui.TeacherRollCallController.doConfirmCancelLectureBlock(TeacherRollCallController.java:668)
   at org.olat.modules.lecture.ui.TeacherRollCallController.formInnerEvent(TeacherRollCallController.java:490)
   at org.olat.core.gui.components.form.flexible.impl.FormBasicController.event(FormBasicController.java:421)
   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)