```
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
else
                        {
                            if constexpr (IsDataTypeDecimal<FromDataType> && IsDataTypeDecimal<ToDataType>)
                                vec_to[i] = convertDecimals<FromDataType, ToDataType>(vec_from[i], vec_from.getScale(), vec_to.getScale());
                            else if constexpr (IsDataTypeDecimal<FromDataType> && IsDataTypeNumber<ToDataType>)
                                vec_to[i] = convertFromDecimal<FromDataType, ToDataType>(vec_from[i], vec_from.getScale());
                            else if constexpr (IsDataTypeNumber<FromDataType> && IsDataTypeDecimal<ToDataType>)
                                vec_to[i] = convertToDecimal<FromDataType, ToDataType>(vec_from[i], vec_to.getScale());
                            else
                                throw Exception("Unsupported data type in conversion function", ErrorCodes::CANNOT_CONVERT_TYPE);
                        }
                    }
                    else
                    {
                        
                        if constexpr (std::is_floating_point_v<FromFieldType> && !std::is_floating_point_v<ToFieldType>)
                        {
                            if (!isFinite(vec_from[i]))
                            {
                                if constexpr (std::is_same_v<Additions, AccurateOrNullConvertStrategyAdditions>)
                                {
                                    (*vec_null_map_to)[i] = true;
                                    continue;
                                }
                                else
                                    throw Exception("Unexpected inf or nan to integer conversion", ErrorCodes::CANNOT_CONVERT_TYPE);
                            }
                        }
                        if constexpr (std::is_same_v<Additions, AccurateOrNullConvertStrategyAdditions>
                                || std::is_same_v<Additions, AccurateConvertStrategyAdditions>)