### Godot version

4.1.dev4

### System information

Windows 10 - Godot 4.1.dev4 - Compatibility

### Issue description

When you syncronize 2 variables and both are in watched mode (taking out the "sync" property too) the server crashes

### Steps to reproduce

Create a MultiplayerSynchronizer, export 2 variables from a script, connect the server and the client and the server will crash instantly

In the project I give, the server and client are connected automatically when you use 2 debug instances when pressing play

### Minimal reproduction project

[minimalproject.zip](https://github.com/godotengine/godot/files/11665652/minimalproject.zip)

ERR_FAIL_COND_V(!node, ERR_UNAUTHORIZED);
	node->set_name(name);
	
	ERR_FAIL_COND_V(!peers_info.has(p_from), ERR_UNAVAILABLE);
	ERR_FAIL_COND_V(peers_info[p_from].recv_nodes.has(net_id), ERR_ALREADY_IN_USE);
	ObjectID oid = node->get_instance_id();
	TrackedNode &tobj = _track(oid);
	tobj.spawner = spawner->get_instance_id();
	tobj.net_id = net_id;
	tobj.remote_peer = p_from;
	peers_info[p_from].recv_nodes[net_id] = oid;
	
	pending_spawn = node->get_instance_id();
	pending_spawn_remote = p_from;
	pending_buffer_size = p_buffer_len - ofs;
	pending_buffer = pending_buffer_size > 0 ? &p_buffer[ofs] : nullptr;
	pending_sync_net_ids = sync_ids;
	parent->add_child(node);
	spawner->emit_signal(SNAME("spawned"), node);
	pending_spawn = ObjectID();
	pending_spawn_remote = 0;
	pending_buffer = nullptr;
	pending_buffer_size = 0;
	if (pending_sync_net_ids.size()) {
		pending_sync_net_ids.clear();
		ERR_FAIL_V(ERR_INVALID_DATA); 
	}
	return OK;
}
Error SceneReplicationInterface::on_despawn_receive(int p_from, const uint8_t *p_buffer, int p_buffer_len) {