v.21.11Improvements

Fix Nullable Processing in JSON Functions

Fix incorrect Nullable processing of JSON functions. This fixes #29615 . Mark as improvement because https://github.com/ClickHouse/ClickHouse/pull/28012 is not released. #29659 (Amos Bird).
Fixes incorrect handling of Nullable types in JSON functions in ClickHouse.

Why it matters

This improvement resolves an issue where JSON functions did not correctly process Nullable data types, potentially leading to unexpected results or errors when working with JSON data containing nullable values. It enhances reliability and correctness when parsing and querying JSON in ClickHouse.

How to use it

Users benefit from this fix automatically when upgrading to the ClickHouse version including this change. No special configuration is required; JSON functions will now correctly handle Nullable inputs and outputs.