```
select tupleElement(CAST(tuple(1,2),'Tuple(x UInt64, y UInt64)'), 'x') 
-- ok

select tupleElement(CAST(tuple(1,2),'Tuple(x UInt64, y UInt64)'), 'z')

-- fails
-- Code: 10. DB::Exception: Received from localhost:9000. DB::Exception: Tuple doesn't have element with name 'z': While processing tupleElement(CAST((1, 2), 'Tuple(x UInt64, y UInt64)'), 'z'). (NOT_FOUND_COLUMN_IN_BLOCK)
```
Proposal - add the 3rd parameter to the tupleElement function and return it if tuple doesn't have a member.

Why? Tuple comes from object('JSON'), sometimes some fields are missing in some jsons.
#include <base/map.h>
#include <base/range.h>
#include <Common/StringUtils/StringUtils.h>
#include <Columns/ColumnTuple.h>
#include <Core/Field.h>
#include <DataTypes/DataTypeTuple.h>
#include <DataTypes/DataTypeArray.h>
#include <DataTypes/DataTypeFactory.h>
#include <DataTypes/Serializations/SerializationInfo.h>
#include <DataTypes/Serializations/SerializationTuple.h>
#include <DataTypes/Serializations/SerializationNamed.h>
#include <DataTypes/Serializations/SerializationInfoTuple.h>
#include <DataTypes/NestedUtils.h>
#include <Parsers/IAST.h>
#include <Parsers/ASTNameTypePair.h>
#include <Common/assert_cast.h>
#include <Common/quoteString.h>
#include <IO/WriteHelpers.h>
#include <IO/WriteBufferFromString.h>
#include <IO/Operators.h>
namespace DB
{
namespace ErrorCodes
{
    extern const int BAD_ARGUMENTS;