### 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_MSG(p_size < 128, "Sync maximum packet size must be at least 128 bytes.");
	sync_mtu = p_size;
}
int SceneReplicationInterface::get_max_sync_packet_size() const {
	return sync_mtu;
}
void SceneReplicationInterface::set_max_delta_packet_size(int p_size) {
	ERR_FAIL_COND_MSG(p_size < 128, "Sync maximum packet size must be at least 128 bytes.");
	delta_mtu = p_size;
}
int SceneReplicationInterface::get_max_delta_packet_size() const {
	return delta_mtu;
}