```
SELECT
    CAST(([2, 1, 1023], ['', '']), 'Map(UInt8, String)') AS map,
    map[10]
```

Triggers `Assertion 'n < size()' failed` in `DB::ColumnString::operator[](unsigned long)`
https://clickhouse-test-reports.s3.yandex.net/18481/64c4ade5b0e0c9a13d6c2475431daf431fc97554/fuzzer/fuzzer.log

Introduced here: #17829
First found here: #18481
}
                parsed = parsed && isAllRead(read_buffer);
                if (!parsed)
                    vec_to[i] = static_cast<typename ToDataType::FieldType>(0);
                if constexpr (exception_mode == ConvertFromStringExceptionMode::Null)
                    (*vec_null_map_to)[i] = !parsed;
            }
            current_offset = next_offset;
        }
        if constexpr (exception_mode == ConvertFromStringExceptionMode::Null)
            return ColumnNullable::create(std::move(col_to), std::move(col_null_map_to));
        else
            return col_to;
    }
};
template <typename ToDataType, typename Name>
struct ConvertImpl<std::enable_if_t<!std::is_same_v<ToDataType, DataTypeString>, DataTypeString>, ToDataType, Name, ConvertDefaultBehaviorTag>
    : ConvertThroughParsing<DataTypeString, ToDataType, Name, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::Normal> {};
template <typename ToDataType, typename Name>
struct ConvertImpl<std::enable_if_t<!std::is_same_v<ToDataType, DataTypeFixedString>, DataTypeFixedString>, ToDataType, Name, ConvertDefaultBehaviorTag>
    : ConvertThroughParsing<DataTypeFixedString, ToDataType, Name, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::Normal> {};
template <typename ToDataType, typename Name>
struct ConvertImpl<std::enable_if_t<!std::is_same_v<ToDataType, DataTypeString>, DataTypeString>, ToDataType, Name, ConvertReturnNullOnErrorTag>
    : ConvertThroughParsing<DataTypeString, ToDataType, Name, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::Normal> {};
template <typename ToDataType, typename Name>
struct ConvertImpl<std::enable_if_t<!std::is_same_v<ToDataType, DataTypeFixedString>, DataTypeFixedString>, ToDataType, Name, ConvertReturnNullOnErrorTag>
    : ConvertThroughParsing<DataTypeFixedString, ToDataType, Name, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::Normal> {};
struct ConvertImplGenericFromString
{
    static ColumnPtr execute(ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type)