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

return;
    }
    if (has_blocks_with_unknown_bucket)
    {
        LOG_TRACE(log, "Merging partially aggregated single-level data.");
        bool no_more_keys = false;
        BlocksList & blocks = bucket_to_blocks[-1];
        for (Block & block : blocks)
        {
            if (isCancelled())
            {
                result.invalidate();
                return;
            }
            if (!checkLimits(result.sizeWithoutOverflowRow(), no_more_keys))
                break;
            if (result.type == AggregatedDataVariants::Type::without_key || block.info.is_overflows)
                mergeWithoutKeyStreamsImpl(block, result);
        #define M(NAME, IS_TWO_LEVEL) \
            else if (result.type == AggregatedDataVariants::Type::NAME) \
                mergeStreamsImpl(block, result.aggregates_pool, *result.NAME, result.NAME->data, result.without_key, no_more_keys);
            APPLY_FOR_AGGREGATED_VARIANTS(M)
        #undef M
            else if (result.type != AggregatedDataVariants::Type::without_key)
                throw Exception("Unknown aggregated data variant.", ErrorCodes::UNKNOWN_AGGREGATED_DATA_VARIANT);
        }
        LOG_TRACE(log, "Merged partially aggregated single-level data.");
    }
}
Block Aggregator::mergeBlocks(BlocksList & blocks, bool final)