RS close roll call if the minutes field is empty and the "-" reason choosed

2017-10-24 13:02:01,824 [ajp-nio2-8027-exec-15] ERROR OLATRuntimeException - OLAT::ERROR ^%^ N27-E7 ^%^ org.olat.core.logging 

https://lernen.xyz.ch/auth/HomeSite/4816967/mylectures/0/coach/0/LectureBlock/4031
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.100 Safari/537.36
**RedScreen**

<dispatchinfo>
	<componentinfo>
		<compname>ffo_main_null</compname>
		<compclass>org.olat.core.gui.components.form.flexible.impl.FormWrapperContainer</compclass>
		<extendedinfo>n/a</extendedinfo>
		<event>	</event>
	</componentinfo>
	<controllerinfo>	</controllerinfo>
</dispatchinfo>

>>> stack of 1.cause::org.olat.core.logging.OLATRuntimeException: null
-> 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:549)
   at org.olat.core.gui.components.Window.doDispatchRequest(Window.java:242)
   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:289)
   at org.olat.core.servlets.OpenOLATServlet.doPost(OpenOLATServlet.java:232)
   at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
>>> stack of 2.cause::java.lang.NullPointerException: null
-> at org.olat.modules.lecture.ui.CloseRollCallConfirmationController.differentEffectiveEndDate(CloseRollCallConfirmationController.java:247)
   at org.olat.modules.lecture.ui.CloseRollCallConfirmationController.validateFormLogic(CloseRollCallConfirmationController.java:223)
   at org.olat.core.gui.components.form.flexible.impl.Form.submit(Form.java:476)
   at org.olat.core.gui.components.form.flexible.impl.Form.submit(Form.java:451)
   at org.olat.core.gui.components.form.flexible.impl.elements.FormSubmit.dispatchFormRequest(FormSubmit.java:77)
   at org.olat.core.gui.components.form.flexible.impl.FormItemImpl.doDispatchFormRequest(FormItemImpl.java:538)
   at org.olat.core.gui.components.form.flexible.impl.Form.evalFormRequest(Form.java:304)
   at org.olat.core.gui.components.form.flexible.impl.FormWrapperContainer.doDispatchRequest(FormWrapperContainer.java:103)
   at org.olat.core.gui.components.AbstractComponent.dispatchRequest(AbstractComponent.java:193)
   at org.olat.core.gui.components.Window.doDispatchToComponent(Window.java:1143)
   at org.olat.core.gui.components.Window.dispatchRequest(Window.java:358)