### Godot version

4.2 eca6f0e

### System information

Windows 10 x64

### Issue description


https://github.com/godotengine/godot/assets/2223172/a2796263-4e2e-4b14-a080-b3ad034cc141



### Steps to reproduce

1. Add SubViewport
2. Add Sprite2D
3. Set spirte's texture to ViewportTexture
4. Create new scene
5. Instance the new scene inside the scene with viewport
6. Make sure both scenes are opened
7. Go to instance scene and save it
8. Go to viewport scene

You will see error spam. Reloading the scene fixes it.

### Minimal reproduction project

[vip.zip](https://github.com/godotengine/godot/files/12292386/vip.zip)

friend class Resource;
	friend class ResourceLoader; 
	static Mutex lock;
	static HashMap<String, Resource *> resources;
#ifdef TOOLS_ENABLED
	static HashMap<String, HashMap<String, String>> resource_path_cache; 
	static RWLock path_cache_lock;
#endif 
	friend void unregister_core_types();
	static void clear();
	friend void register_core_types();
public:
	static bool has(const String &p_path);
	static Ref<Resource> get_ref(const String &p_path);
	static void get_cached_resources(List<Ref<Resource>> *p_resources);
	static int get_cached_resource_count();
};
#endif