I implemented call forwarding according to https://www.kamailio.org/wiki/tutorials/mini-howto-admin/call_forwarding, which is working fine. When I replace db_mysql with db_mongodb however, I receive an error on "if (avp_db_load("$ruri/username", "$avp(s:fwd_blind)")) {": ERROR: db_mongodb [mongodb_dbase.c:381]: db_mongodb_get_columns(): field [attribute] not found in result iterator ERROR: db_mongodb [mongodb_dbase.c:739]: db_mongodb_store_result(): failed to set the columns ERROR: db_mongodb [mongodb_dbase.c:918]: db_mongodb_query(): failed to store result ERROR: db_mongodb [mongodb_dbase.c:927]: db_mongodb_query(): failed to do the query ERROR: avpops [avpops_impl.c:381]: ops_dbload_avps(): db_load failed