```
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
}
        if (const ColVecFrom * col_from = checkAndGetColumn<ColVecFrom>(named_from.column.get()))
        {
            typename ColVecTo::MutablePtr col_to = nullptr;
            if constexpr (IsDataTypeDecimal<ToDataType>)
            {
                UInt32 scale;
                if constexpr (std::is_same_v<Additions, AccurateConvertStrategyAdditions>
                    || std::is_same_v<Additions, AccurateOrNullConvertStrategyAdditions>)
                {
                    scale = additions.scale;
                }
                else
                {
                    scale = additions;
                }
                col_to = ColVecTo::create(0, scale);
            }
            else
                col_to = ColVecTo::create();
            const auto & vec_from = col_from->getData();
            auto & vec_to = col_to->getData();
            size_t size = vec_from.size();
            vec_to.resize(size);
            ColumnUInt8::MutablePtr col_null_map_to;
            ColumnUInt8::Container * vec_null_map_to [[maybe_unused]] = nullptr;
            if constexpr (std::is_same_v<Additions, AccurateOrNullConvertStrategyAdditions>)
            {
                col_null_map_to = ColumnUInt8::create(size, false);
                vec_null_map_to = &col_null_map_to->getData();