public static ClickHouseInstantValue ofNull(int scale, TimeZone tz) {
        return ofNull(null, scale, tz);
    }
Create a new instance representing null getValue().

@param scale scale
@param tz    time zone, null is treated as {@code UTC}
@return new instance representing null value
clickhouse-data/src/main/java/com/clickhouse/data/value/ClickHouseInstantValue.java