v.21.11Improvements

Fix NULL Column Handling in JSON Functions

Fix misbehavior of NULL column handling in JSON functions. This fixes #27930. #28012 (Amos Bird).
Fixes incorrect handling of NULL values in JSON functions within ClickHouse.

Why it matters

This feature addresses a bug where JSON functions did not properly handle NULL columns, leading to incorrect or unexpected results. Resolving this issue improves data accuracy and reliability when working with JSON data containing NULL values.

How to use it

Users benefit from this fix automatically after upgrading to the version containing the patch. No additional configuration or changes to queries are required; JSON functions will correctly process NULL columns as expected.