**Describe the bug**
```
SELECT number % 100 AS k, sumArray(emptyArrayUInt8()) AS v FROM numbers(10) GROUP BY k
```
Fails under ASan.

{
    if (blocks.empty())
        return {};
    auto bucket_num = blocks.front().info.bucket_num;
    bool is_overflows = blocks.front().info.is_overflows;
    LOG_TRACE(log, "Merging partially aggregated blocks (bucket = {}).", bucket_num);
    Stopwatch watch;
    /** If possible, change 'method' to some_hash64. Otherwise, leave as is.
      * Better hash function is needed because during external aggregation,
      *  we may merge partitions of data with total number of keys far greater than 4 billion.
      */
    auto merge_method = method_chosen;
#define APPLY_FOR_VARIANTS_THAT_MAY_USE_BETTER_HASH_FUNCTION(M) \
        M(key64)            \
        M(key_string)       \