### 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_oid)) {
		return true; 
	}
	ERR_FAIL_COND_V(p_peer < 0, false);
	const TrackedNode &tnode = tracked_nodes[p_oid];
	if (tnode.synchronizers.is_empty()) {
		return true; 
	}
	if (tnode.remote_peer && uint32_t(p_peer) == tnode.remote_peer) {
		return true; 
	} else if (spawned_nodes.has(p_oid)) {
		
		if (p_peer) {
			return peers_info.has(p_peer) && peers_info[p_peer].spawn_nodes.has(p_oid);
		} else {
			for (const KeyValue<int, PeerInfo> &E : peers_info) {
				if (!E.value.spawn_nodes.has(p_oid)) {
					return false; 
				}
			}
			return true; 
		}
	} else {
		
		for (const ObjectID &sid : tnode.synchronizers) {
			MultiplayerSynchronizer *sync = get_id_as<MultiplayerSynchronizer>(sid);
			ERR_CONTINUE(!sync);