Error retrieving JSON data as 'json?' type when entry is null

[sanduninduwara]

Description:
When there is a PostgreSQL database table entry that includes a JSON-type record(This entry can be null). When the entry is null and trying to retrieve the JSON data as a 'json?' type, It gives an error message. However, when that entry is retrieved as a 'string?' type, it won't encounter any errors.

Error message:
error: Error when iterating through the SQL result. null

OS, DB, other environment details and versions:
database connector ballerinax/postgresql