### 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)

const ObjectID oid = p_node->get_instance_id();
	const TrackedNode *tnode = tracked_nodes.getptr(oid);
	ERR_FAIL_COND_V(!tnode, ERR_INVALID_PARAMETER);
	MAKE_ROOM(5);
	uint8_t *ptr = packet_cache.ptrw();
	ptr[0] = (uint8_t)SceneMultiplayer::NETWORK_COMMAND_DESPAWN;
	int ofs = 1;
	uint32_t nid = tnode->net_id;
	ofs += encode_uint32(nid, &ptr[ofs]);
	r_len = ofs;
	return OK;
}
Error SceneReplicationInterface::on_spawn_receive(int p_from, const uint8_t *p_buffer, int p_buffer_len) {
	ERR_FAIL_COND_V_MSG(p_buffer_len < 18, ERR_INVALID_DATA, "Invalid spawn packet received");
	int ofs = 1; 
	uint8_t scene_id = p_buffer[ofs];
	ofs += 1;
	uint32_t node_target = decode_uint32(&p_buffer[ofs]);
	ofs += 4;
	MultiplayerSpawner *spawner = Object::cast_to<MultiplayerSpawner>(multiplayer->get_path_cache()->get_cached_object(p_from, node_target));
	ERR_FAIL_COND_V(!spawner, ERR_DOES_NOT_EXIST);
	ERR_FAIL_COND_V(p_from != spawner->get_multiplayer_authority(), ERR_UNAUTHORIZED);
	uint32_t net_id = decode_uint32(&p_buffer[ofs]);
	ofs += 4;
	uint32_t sync_len = decode_uint32(&p_buffer[ofs]);
	ofs += 4;
	uint32_t name_len = decode_uint32(&p_buffer[ofs]);
	ofs += 4;
	ERR_FAIL_COND_V_MSG(name_len + (sync_len * 4) > uint32_t(p_buffer_len - ofs), ERR_INVALID_DATA, vformat("Invalid spawn packet size: %d, wants: %d", p_buffer_len, ofs + name_len + (sync_len * 4)));