PA_Properties Application exception in Portal

PA_Properties Application exception in Portal pops up and Portal pages wont be visible after startup. Recently while performing a Portal migration from v6.1 to v8.5, i had faced this strange error where portal starts up properly but as soon as it starts up it throws PA_Properties application related exception as mentioned below.

00000120 ServletWrappe E com.ibm.ws.webcontainer.servlet.ServletWrapper service CWSRV0068E: An exception was thrown by one of the service methods of the servlet [/WEB-INF/properties/html/placeLabelAttribute.jsp] in application [PA_Properties]. Exception created : [java.lang.NullPointerException
at com.ibm.wps.portlets.properties.utils.MetaDataFilter.accept(MetaDataFilter.java:42)
at com.ibm.wps.portlets.properties.utils.PropertiesContextInfo.canShowThemePolicy(PropertiesContextInfo.java:895)
at com.ibm._jsp._placeLabelAttribute._jspService(_placeLabelAttribute.java:497)
at com.ibm.ws.jsp.runtime.HttpJspBase.service(HttpJspBase.java:99)

00000125 Servlet       E com.ibm.wps.engine.Servlet doGet EJPEJ0004E: An unexpected exception occurred.
com.ibm.portal.state.phases.exceptions.PhaseException:EJPEI0105E: An error occurred during the rendering in phase
[com.ibm.wps.engine.phases.WPRenderPhase@df3a9bc3].

I tried to troubleshoot and could fix the issue by performing the following,

1. From deployment manager console, take a backup of the PA_Properties application backup and then redelpoy the war file from PortalServer applications directory. It solved the issue partially as the exception was lost and I could see portal server up and running.

2. After trying above option 1 and logging into console, I could see the pages getting distorted and also the theme is throwing exceptions. I have removed the current Custom client theme from default one and selected Portal85 theme as custom theme. It worked and then after making the Custom theme as default, everything worked perfectly.