**How to reproduce**
```
$ build_debug/programs/clickhouse local --query "SELECT DISTINCT NULL, if(number > 0, 't', '') AS res FROM numbers(1) ORDER BY res"
clickhouse: /home/milovidov/work/ClickHouse/src/Common/HashTable/HashTableKeyHolder.h:92: void keyHolderPersistKey(DB::ArenaKeyHolder &): Assertion `holder.key.size > 0' failed.
```

https://s3.amazonaws.com/clickhouse-test-reports/44824/6e946cc75779980b65804c70898beaee3d2e621e/fuzzer_astfuzzerdebug/report.html

See https://aretestsgreenyet.com/
Key,
                                          ClearableHashTableCell<Key, HashSetCellWithSavedHash<Key, Hash, ClearableHashSetState>>,
                                          Hash,
                                          Grower,
                                          Allocator>
{
public:
    void clear()
    {
        ++this->version;
        this->m_size = 0;
    }
};
template <typename Key, typename Hash, size_t initial_size_degree>
using ClearableHashSetWithStackMemory = ClearableHashSet<
    Key,
    Hash,
    HashTableGrower<initial_size_degree>,
    HashTableAllocatorWithStackMemory<
        (1ULL << initial_size_degree) * sizeof(ClearableHashTableCell<Key, HashTableCell<Key, Hash, ClearableHashSetState>>)>>;