### 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)

r_net_id = p_sync->get_net_id();
	if (r_net_id == 0 || (r_net_id & 0x80000000)) {
		int path_id = 0;
		bool verified = multiplayer->get_path_cache()->send_object_cache(p_sync, p_peer, path_id);
		ERR_FAIL_COND_V_MSG(path_id < 0, false, "This should never happen!");
		if (r_net_id == 0) {
			
			r_net_id = path_id | 0x80000000;
			p_sync->set_net_id(r_net_id | 0x80000000);
		}
		return verified;
	}
	return true;
}
MultiplayerSynchronizer *SceneReplicationInterface::_find_synchronizer(int p_peer, uint32_t p_net_id) {
	MultiplayerSynchronizer *sync = nullptr;
	if (p_net_id & 0x80000000) {
		sync = Object::cast_to<MultiplayerSynchronizer>(multiplayer->get_path_cache()->get_cached_object(p_peer, p_net_id & 0x7FFFFFFF));
	} else if (peers_info[p_peer].recv_sync_ids.has(p_net_id)) {
		const ObjectID &sid = peers_info[p_peer].recv_sync_ids[p_net_id];
		sync = get_id_as<MultiplayerSynchronizer>(sid);
	}
	return sync;
}
void SceneReplicationInterface::_send_delta(int p_peer, const HashSet<ObjectID> p_synchronizers, uint64_t p_usec, const HashMap<ObjectID, uint64_t> p_last_watch_usecs) {