SQLSTATE of notice PGresult

Hey all,

Accordingly to the documentation of libpq, SQLSTATE code field "is not
localizable, and
is always present.". But it seems, in some cases it isn't. E.g.

/* the main code */
PGresult* res = Pg::PQexec(conn, "select 1");
Oid id = PQparamtype(res, 1);

/* the notice receiver */
void myNoticeReceiver(void *arg, const PGresult *res)
{
/* Presents - "NOTICE" */
const char* severity = Pg::PQresultErrorField(res, PG_DIAG_SEVERITY);

/* NOT presents - NULL. Why not "00000" ? */
const char* sqlstate = Pg::PQresultErrorField(res, PG_DIAG_SQLSTATE);

/* Presents - "parameter number 1 is out of range 0..-1" */
const char* primary = Pg::PQresultErrorField(res,
PG_DIAG_MESSAGE_PRIMARY);
}

So, SQLSTATE field is not always presents.

Regards,
Dmitriy