I expect it should work:
```
:) select CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))')

SELECT CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))')

Query id: fb057b45-b72a-4d22-9b38-a3136cdf2465


0 rows in set. Elapsed: 0.002 sec.

Received exception from server (version 22.5.1):
Code: 53. DB::Exception: Received from localhost:9000. DB::Exception: Cast to Object can be performed only from flatten named Tuple, Map or String. Got: Object('json'): While processing CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))'). (TYPE_MISMATCH)
```

@CurtizJ what do you think?
for (size_t row = 0; row < offsets.size(); ++row)
            {
                for (size_t i = offsets[static_cast<ssize_t>(row) - 1]; i < offsets[row]; ++i)
                {
                    auto ref = key_column_str.getDataAt(i);
                    bool inserted;
                    SubcolumnsMap::LookupResult it;
                    subcolumns.emplace(ref, it, inserted);
                    auto & subcolumn = it->getMapped();
                    if (inserted)
                        subcolumn = value_column.cloneEmpty()->cloneResized(row);
                    
                    if (subcolumn->size() == row)
                        subcolumn->insertFrom(value_column, i);
                }
                
                for (const auto & [_, subcolumn] : subcolumns)
                    if (subcolumn->size() == row)
                        subcolumn->insertDefault();
            }
            auto column_object = ColumnObject::create(has_nullable_subcolumns);
            for (auto && [key, subcolumn] : subcolumns)
            {
                PathInData path(key.toView());
                column_object->addSubcolumn(path, std::move(subcolumn));
            }
            return column_object;
        };
    }
    WrapperType createObjectWrapper(const DataTypePtr & from_type, const DataTypeObject * to_type) const