If not implemented, null should not be returned

[nieqiurong]

https://github.com/ClickHouse/clickhouse-java/blob/7a139706364f2888450405542e8a3df0589653ee/jdbc-v2/src/main/java/com/clickhouse/jdbc/metadata/DatabaseMetaData.java#L1029C1-L1032C1

I see that there are two implementations in the driver package, and the other ClickHouseBaseMetaData implements the getIndexInfo logic, but the implementation of DatabaseMetaData returns null. It would be better to return an empty ResultSet

[chernser]

Good day, @nieqiurong!
Thank you for reporting it!