**How to reproduce**
Clickhouse version 20.11.5.18, 20.8.7.15, 20.3.19
```
SELECT
    groupUniqArray(val) AS uniq,
    toTypeName(uniq),
    groupArray(val) AS arr,
    toTypeName(arr)
FROM
(
    SELECT CAST(number % 2, 'Enum(\'hello\' = 1, \'world\' = 0)') AS val
    FROM numbers(2)
)

Query id: d4657f27-c8bd-4174-9947-c6c48d0222d5

┌─uniq──┬─toTypeName(groupUniqArray(val))─┬─arr───────────────┬─toTypeName(groupArray(val))────────────┐
│ [0,1] │ Array(Int8)                     │ ['world','hello'] │ Array(Enum8('world' = 0, 'hello' = 1)) │
└───────┴─────────────────────────────────┴───────────────────┴────────────────────────────────────────┘
```

{
        if constexpr (Trait::sampler == Sampler::NONE)
        {
            auto & cur_elems = this->data(place);
            auto & rhs_elems = this->data(rhs);
            if (!limit_num_elems)
            {
                if (rhs_elems.value.size())
                    cur_elems.value.insertByOffsets(rhs_elems.value, 0, rhs_elems.value.size(), arena);
            }
            else
            {
                UInt64 elems_to_insert = std::min(static_cast<size_t>(max_elems) - cur_elems.value.size(), rhs_elems.value.size());
                if (elems_to_insert)
                    cur_elems.value.insertByOffsets(rhs_elems.value, 0, elems_to_insert, arena);
            }
        }
        if constexpr (Trait::sampler == Sampler::RNG)
        {
            if (this->data(rhs).value.empty()) 
                return;
            auto & a = this->data(place);
            auto & b = this->data(rhs);