### 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)

if (!tracked_nodes.has(p_id)) {
		tracked_nodes[p_id] = TrackedNode(p_id);
		Node *node = get_id_as<Node>(p_id);
		node->connect(SceneStringNames::get_singleton()->tree_exited, callable_mp(this, &SceneReplicationInterface::_untrack).bind(p_id), Node::CONNECT_ONE_SHOT);
	}
	return tracked_nodes[p_id];
}
void SceneReplicationInterface::_untrack(const ObjectID &p_id) {
	if (!tracked_nodes.has(p_id)) {
		return;
	}
	uint32_t net_id = tracked_nodes[p_id].net_id;
	uint32_t peer = tracked_nodes[p_id].remote_peer;
	tracked_nodes.erase(p_id);
	
	if (peer && peers_info.has(peer)) {
		peers_info[peer].recv_nodes.erase(net_id);
	}
	
	if (net_id || peer == 0) {
		for (KeyValue<int, PeerInfo> &E : peers_info) {
			E.value.spawn_nodes.erase(p_id);
		}
	}
}
void SceneReplicationInterface::_free_remotes(const PeerInfo &p_info) {