### 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)

to_spawn.insert(E.key);
			} else {
				
				_update_spawn_visibility(E.key, p_oid);
			}
		}
	}
	if (to_spawn.size()) {
		int len = 0;
		_make_spawn_packet(node, spawner, len);
		for (int pid : to_spawn) {
			ERR_CONTINUE(!peers_info.has(pid));
			int path_id;
			multiplayer->get_path_cache()->send_object_cache(spawner, pid, path_id);
			_send_raw(packet_cache.ptr(), len, pid, true);
			peers_info[pid].spawn_nodes.insert(p_oid);
		}
	}
	if (to_despawn.size()) {
		int len = 0;
		_make_despawn_packet(node, len);
		for (int pid : to_despawn) {
			ERR_CONTINUE(!peers_info.has(pid));
			peers_info[pid].spawn_nodes.erase(p_oid);
			_send_raw(packet_cache.ptr(), len, pid, true);
		}
	}
	return OK;
}
Error SceneReplicationInterface::_send_raw(const uint8_t *p_buffer, int p_size, int p_peer, bool p_reliable) {