Root cause:

java.lang.IllegalStateException: Attempt to set model object on null model of component: root:tabs:panel-container:cards:2:panel:center:tabs:panel-container:cards:0:panel:editor:extension.editor:form:template:layout.form:list:item:30:item-container:field-link:field:other-radio-group
at org.apache.wicket.Component.setDefaultModelObject(Component.java:3058)
at org.apache.wicket.markup.html.form.FormComponent.setModelObject(FormComponent.java:1578)
at org.apache.wicket.markup.html.form.FormComponent.updateModel(FormComponent.java:1104)
at org.apache.wicket.markup.html.form.Form$FormModelUpdateVisitor.component(Form.java:228)
at org.apache.wicket.markup.html.form.Form$FormModelUpdateVisitor.component(Form.java:198)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:274)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrderHelper(Visits.java:262)
at org.apache.wicket.util.visit.Visits.visitPostOrder(Visits.java:245)
at org.apache.wicket.markup.html.form.FormComponent.visitComponentsPostOrder(FormComponent.java:430)
at org.apache.wicket.markup.html.form.Form.internalUpdateFormComponentModels(Form.java:1814)
at org.apache.wicket.markup.html.form.Form.updateFormComponentModels(Form.java:1778)
at org.apache.wicket.markup.html.form.Form.process(Form.java:927)
at org.apache.wicket.markup.html.form.Form.onFormSubmitted(Form.java:770)
at org.apache.wicket.ajax.form.AjaxFormSubmitBehavior.onEvent(AjaxFormSubmitBehavior.java:156)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:123)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:626)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:258)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:241)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:250)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:236)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:862)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)
at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:201)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:282)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:315)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)

Complete stack:

org.apache.wicket.WicketRuntimeException: Method onRequest of interface org.apache.wicket.behavior.IBehaviorListener targeted at org.hippoecm.addon.workflow.MenuLink$1@14e287c on component [MenuLink [Component id = link]] threw an exception
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:268)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:241)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:250)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:236)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:862)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)

java.lang.reflect.InvocationTargetException
at sun.reflect.GeneratedMethodAccessor108.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.wicket.RequestListenerInterface.internalInvoke(RequestListenerInterface.java:258)
at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:241)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.invokeListener(ListenerInterfaceRequestHandler.java:250)
at org.apache.wicket.core.request.handler.ListenerInterfaceRequestHandler.respond(ListenerInterfaceRequestHandler.java:236)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:862)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)