Entt: registry::clone doesn't copy the remove delegate

[skypjack]

Within registry::clone, the remove delegate isn't neither copied nor initialized. Some functionalities are therefore unavailable or risky for the newly returned registry.

[jspdown]

Just encountered the issue. It's impossible to use registry.destroy on a copied registry.

Can be reproduced with:

#include <iostream>
#include <entt/entt.hpp>

struct component {};

int main() {
  entt::registry reg;

  auto entity = reg.create();
  reg.assign<component>(entity);

  auto new_reg = reg.clone();
  auto view = new_reg.view<component>();

  for (auto e : view) {
    new_reg.destroy(e); // segfault here
  }
}

gdb backtrace:

(gdb) backtrace
#0  0x0000000000000000 in ?? ()
#1  0x0000555555557c39 in entt::basic_registry<unsigned int>::destroy (entity=0, this=0x7fffffffdee0) at /usr/local/include/entt/entity/registry.hpp:664
#2  main () at test.cpp:16

Tested on EnTT v3.0.0

[skypjack]

Yep, this is the whole point of the issue.
I've already added a dedicated test locally for this yesterday but I've not the time to fix it right now.
I'll push the changes upstream soon and probably cut a v3.1.0 because of some other features already released. :+1: