ejabberd mod_multicast error

I am using the mod_multicast(XEP-0033) in ejabberd, But I get the error "mod_multicast:handle_info:176 Error when processing IQ stanza: {{case_clause,<<"jabber:iq:roster">>},[{mod_multicast,process_iqreply_result,4,[{file,"src/mod_multicast.erl"},{line,738}]},{mod_multicast,handle_info,2,[{file,"src/mod_multicast.erl"},{line,174}]},{gen_server,try_dispatch,4,[{file,"gen_server.erl"},{line,593}]},{gen_server,handle_msg,5,[{file,"gen_server.erl"},{line,659}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,237}]}]}". who can help me? Thank you first. The JAVA code is MultipleRecipientManager.send( connection, message, list, null, null, null,null,false );