unordered set node undefined behavior

Im trying to use vector of buckets for dynamic extension.

My code:

```cpp
buckets.resize(buckets.size() * 2);
myset.rehash({buckets.data(), buckets.size()});
```

Code compiles, but it is undefined behavior and ... Thats why:

detail/hashtable_node.hpp:

```cpp
inline bucket_impl()
{}

inline bucket_impl(const bucket_impl &)
{}

inline ~bucket_impl()
{}
```

Copy constructor(its move ctor too) does nothing and its even not noexcept, so vector .resize creates invalid nodes, then .rehash works with invalid memory = segfault

..Why? And how to do it correctly?