NullPointerException when calling REST MOP export feature for custom portal in EPP 5

Issue

• NullPointerException is thrown when I call MOP export via REST.

2015-08-13 15:36:24,951 DEBUG [org.gatein.management.core.api.controller.SimpleManagementController] (http-10.174.74.32-8443-1) Executing request for operation export-resource at address /mop/usersites
2015-08-13 15:36:24,969 ERROR [org.gatein.management.rest.providers.ManagedComponentProvider] (http-10.174.74.32-8443-1) Exception marshalling entity class org.gatein.management.api.operation.model.ExportResourceModel for media type application/zip
org.gatein.management.api.binding.BindingException: Exception writing data to zip.
        at org.gatein.management.core.api.binding.zip.ExportResourceModelMarshaller.marshal(ExportResourceModelMarshaller.java:88)
        at org.gatein.management.core.api.binding.zip.ExportResourceModelMarshaller.marshal(ExportResourceModelMarshaller.java:47)
        at org.gatein.management.rest.providers.ManagedComponentProvider.writeTo(ManagedComponentProvider.java:99)
        at org.exoplatform.services.rest.servlet.RestServlet$ServletContainerResponseWriter.writeBody(RestServlet.java:138)
        at org.exoplatform.services.rest.impl.ContainerResponse.writeResponse(ContainerResponse.java:211)
        at org.exoplatform.services.rest.impl.RequestHandlerImpl.handleRequest(RequestHandlerImpl.java:242)
        at org.exoplatform.services.rest.servlet.RestServlet.onService(RestServlet.java:85)
...
Caused by: java.lang.NullPointerException
        at com.ctc.wstx.sw.BaseStreamWriter.writeCharacters(BaseStreamWriter.java:498)
        at org.gatein.common.xml.stax.writer.StaxWriterImpl$StreamElement$4.execute(StaxWriterImpl.java:438)
        at org.gatein.common.xml.stax.writer.StaxWriterImpl$Element.apply(StaxWriterImpl.java:225)
        at org.gatein.common.xml.stax.writer.StaxWriterImpl$StreamElement.writeContent(StaxWriterImpl.java:434)
        at org.gatein.common.xml.stax.writer.StaxWriterImpl.writeContent(StaxWriterImpl.java:132)
        at org.gatein.common.xml.stax.writer.StaxWriterImpl.writeElement(StaxWriterImpl.java:144)
        at org.gatein.common.xml.stax.writer.StaxWriterUtils.writeOptionalElement(StaxWriterUtils.java:141)
        at org.exoplatform.portal.mop.management.binding.xml.AbstractMarshaller.marshalAccessPermissions(AbstractMarshaller.java:613)
        at org.exoplatform.portal.mop.management.binding.xml.PageMarshaller.marshalPage(PageMarshaller.java:137)
        at org.exoplatform.portal.mop.management.binding.xml.PageMarshaller.marshal(PageMarshaller.java:64)
        at org.exoplatform.portal.mop.management.binding.xml.PageMarshaller.marshal(PageMarshaller.java:49)
        at org.exoplatform.portal.mop.management.exportimport.PageExportTask.export(PageExportTask.java:77)
        at org.gatein.management.core.api.binding.zip.ExportResourceModelMarshaller.marshal(ExportResourceModelMarshaller.java:78)
        ... 40 more