**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 (!data(rhs).first) 
            return;
        UInt64 new_elems;
        UInt64 cur_elems = data(place).elems;
        if (limit_num_elems)
        {
            if (data(place).elems >= max_elems)
                return;
            new_elems = std::min(data(place).elems + data(rhs).elems, static_cast<size_t>(max_elems));
        }
        else
        {
            new_elems = data(place).elems + data(rhs).elems;
        }
        Node * p_rhs = data(rhs).first;
        Node * p_lhs;
        if (unlikely(!data(place).last)) 
        {
            p_lhs = p_rhs->clone(arena);