3528305 - while trying to invoke the method java.lang.Object.equals(java.lang.Object) of a null object returned from com.sap.portal.admin.editor.EditorContext.getProperty

When accessing Available Components from URL "https://<hostname>:<port>/irj/servlet/prt/portal/prtroot/", then click on a component, such as  "TrainEditor" in this case,  error message shown as following:

From defaultTrace you can see:

[EXCEPTION]
com.sapportals.portal.prt.component.PortalComponentException: Error in service call of Portal Component
Application name : com.sap.portal.admin.editorframework
Component : com.sap.portal.admin.editorframework.TrainEditor
Component class : com.sap.portal.admin.editor.example.train.TrainEditor
User : xxxx
at com.sap.portal.prt.core.PortalRequestManager.handlePortalComponentException(PortalRequestManager.java:780)
at com.sap.portal.prt.core.PortalRequestManager.callPortalComponent(PortalRequestManager.java:234)
at com.sap.portal.prt.core.PortalRequestManager.dispatchRequest(PortalRequestManager.java:96)
at com.sap.portal.prt.core.PortalRequestManager.dispatchRequest(PortalRequestManager.java:130)
at com.sap.portal.prt.component.PortalComponentResponse.include(PortalComponentResponse.java:206)
at com.sap.portal.prt.pom.PortalNode.service(PortalNode.java:590)
at com.sap.portal.prt.core.PortalRequestManager.callPortalComponent(PortalRequestManager.java:222)
at com.sap.portal.prt.core.PortalRequestManager.dispatchRequest(PortalRequestManager.java:96)
at com.sap.portal.prt.core.PortalRequestManager.dispatchRequest(PortalRequestManager.java:130)
at com.sap.portal.prt.core.PortalRequestManager.runRequestCycle(PortalRequestManager.java:509)
at com.sapportals.portal.prt.connection.ServletConnection._handleRequest(ServletConnection.java:224)
at com.sapportals.portal.prt.connection.ServletConnection.handleRequest(ServletConnection.java:101)
at com.sap.portal.prt.dispatcher.DispatcherServlet.service(DispatcherServlet.java:132)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
(…)
Caused by: java.lang.NullPointerException: while trying to invoke the method java.lang.Object.equals(java.lang.Object) of a null object returned from com.sap.portal.admin.editor.EditorContext.getProperty(java.lang.String)
at com.sap.portal.admin.editor.pane.OutPane.calculatePEObjectId(OutPane.java:210)
(…)

• SAP NetWeaver Enterprise Portal

java.lang.NullPointerException: while trying to invoke the method java.lang.Object.equals(java.lang.Object) of a null object returned from com.sap.portal.admin.editor.EditorContext.getProperty(java.lang.String), portal runtime error, irj/servlet/prt/portal/prtroot/, TrainEditor , KBA , EP-PIN-PRT , Portal Runtime , Problem