field->catalog is undefined when obtained from prepared statement resultset

static int test_stmt_fields(MYSQL *mysql)

{

  char *query= "SELECT a FROM t1";

  MYSQL_RES *res;

  MYSQL_STMT *stmt;

  MYSQL_FIELD *fields;

  int rc;

  rc= mysql_query(mysql, "DROP TABLE IF EXISTS t1");

  check_mysql_rc(rc, mysql);

  rc= mysql_query(mysql, "CREATE TABLE t1 (a int)");

  check_mysql_rc(rc, mysql);

  rc= mysql_query(mysql, "INSERT INTO t1 VALUES (1)");

  check_mysql_rc(rc, mysql);

  stmt= mysql_stmt_init(mysql);

  FAIL_IF(!stmt, "couldn't allocate memory");

  rc= mysql_stmt_prepare(stmt, query, strlen(query));

  check_stmt_rc(rc, stmt);

  rc= mysql_stmt_execute(stmt);

  check_stmt_rc(rc, stmt);

  res= mysql_stmt_result_metadata(stmt);

  FAIL_IF(!res, "Can't obtain resultset");

  fields= mysql_fetch_fields(res);

  FAIL_IF(!fields, "Can't obtain fields");

  FAIL_IF(strcmp("def", fields[0].catalog), "unexpected value for field->catalog");

  mysql_free_result(res);

  mysql_stmt_close(stmt);

}