Error 42000

U0002: The object "(NULL)" does not exist.
in
signal:(BIF),
        __01 => '42000',
        __02 => 'The object "(NULL)" does not exist.',
        __03 => 'U0002',
DB.DBA.GET_SEC_OBJECT_ID([executable]/users.sql:185),
       _name => '(NULL)',
          id => 0,
      is_sql => 0,
        opts => 0,
DB.DBA.USER_GET_OPTION([executable]/users.sql:673),
       _name => '(NULL)',
         opt => 'SIOC_POSTS_QUERY_LIMIT',
sioc.DBA.compose_foaf:42,
      u_name => '(NULL)',
      accept => 'application/rdf+xml',
           p => 0,
DB.DBA.RDFData_DAV_RES_CONTENT([executable]/DET_RDFData.sql:601),
          id => (ARRAY_OF_POINTER value, tag 193),
     content => (STRING_SESSION value, tag 185),
        type => 'application/rdf+xml',
  content_mode => 1,
DB.DBA.DAV_RES_CONTENT_INT([executable]/dav_api.sql:5876),
          id => (ARRAY_OF_POINTER value, tag 193),
     content => (STRING_SESSION value, tag 185),
        type => 'application/rdf+xml',
  content_mode => 1,
      extern => 0,
  auth_uname => NULL,
    auth_pwd => NULL,
WS.WS.GET([executable]/dav.sql:2995),
        path => (ARRAY_OF_POINTER value, tag 193),
      params => (ARRAY_OF_POINTER value, tag 193),
       lines => (ARRAY_OF_POINTER value, tag 193)