GetNullPionter when Passing noder in setpermission()

Hi,

I am Using Alfresco Community edition 5.0.d, through java api I am trying set permissions ,Using new PermissionServicImpl.setPermission(noderef,authrty,permissin,true) when i run this I getting null pionter execptions .please let help on this issue

NodeRef noder =new NodeRef("workspace://SpacesStore/2f1f1e4a-349d-46dd-86ba-0db9c8f92fcb");

permissionService.setPermission(noder, "muddappa-venkatesh", PermissionService.CONSUMER, true);

Exception in thread "main" java.lang.NullPointerException
at org.alfresco.repo.security.permissions.impl.PermissionServiceImpl.getInheritParentPermissions(PermissionServiceImpl.java:538)
at com.helper.Test.main(Test.java:73)