wicket 出现了一个问题，帮忙看一下

at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:193)
        at org.apache.wicket.request.target.component.listener.ListenerInterfaceRequestTarget.processEvents(ListenerInterfaceRequestTarget.java:73)
        at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:92)
        at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1250)
        at org.apache.wicket.RequestCycle.step(RequestCycle.java:1329)
        at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1428)
        at org.apache.wicket.RequestCycle.request(RequestCycle.java:545)
        at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:479)
        at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:312)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:246)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:313)
        at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:287)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:218)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:94)
        at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:98)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:222)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:166)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:648)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:593)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:587)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:1096)
        at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:288)
        at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.invokeAdapter(DefaultProcessorTask.java:647)
        at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.doProcess(DefaultProcessorTask.java:579)
        at com.sun.enterprise.web.connector.grizzly.DefaultProcessorTask.process(DefaultProcessorTask.java:831)
        at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.executeProcessorTask(DefaultReadTask.java:341)
        at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:263)
        at com.sun.enterprise.web.connector.grizzly.DefaultReadTask.doTask(DefaultReadTask.java:214)
        at com.sun.enterprise.web.portunif.PortUnificationPipeline$PUTask.doTask(PortUnificationPipeline.java:380)
        at com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:265)
        at com.sun.enterprise.web.connector.grizzly.ssl.SSLWorkerThread.run(SSLWorkerThread.java:106)
Caused by: java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.apache.wicket.RequestListenerInterface.invoke(RequestListenerInterface.java:182)
        ... 37 more
Caused by: java.lang.IllegalStateException: Attempt to set model object on null model of component: myregform:ddcusersex
        at org.apache.wicket.Component.setDefaultModelObject(Component.java:3033)
        at org.apache.wicket.up.html.form.FormComponent.updateModel(FormComponent.java:1168)
        at org.apache.wicket.up.html.form.Form$FormModelUpdateVisitor.component(Form.java:227)
        at org.apache.wicket.up.html.form.FormComponent.visitComponentsPostOrderHelper(FormComponent.java:514)
        at org.apache.wicket.up.html.form.FormComponent.visitComponentsPostOrderHelper(FormComponent.java:493)
        at org.apache.wicket.up.html.form.FormComponent.visitComponentsPostOrder(FormComponent.java:465)
        at org.apache.wicket.up.html.form.Form.internalUpdateFormComponentModels(Form.java:2081)
        at org.apache.wicket.up.html.form.Form.updateFormComponentModels(Form.java:2049)
        at org.apache.wicket.up.html.form.Form.process(Form.java:1004)
        at org.apache.wicket.up.html.form.Form.process(Form.java:931)
        at org.apache.wicket.up.html.form.Form.onFormSubmitted(Form.java:896)
        ... 42 more