### Godot version

v4.0 rc6

### System information

Windows 10

### Issue description

When using a ViewportTexture from a SubViewport on a TextureRect, it throws errors after running the scene once and then switching scenes in the editor.
![Pasted image 20230227212626](https://user-images.githubusercontent.com/44676282/221680047-984fa03e-33d1-4856-9a7f-1700b28423cf.png)


### Steps to reproduce

Run the canvas-scene once.
Switch to another scene in the editor.
Switch back to the canvas-scene

### Minimal reproduction project

[ViewportTextureError.zip](https://github.com/godotengine/godot/files/10844099/ViewportTextureError.zip)

Ref<Resource> ref;
	lock.lock();
	Resource **res = resources.getptr(p_path);
	if (res) {
		ref = Ref<Resource>(*res);
	}
	if (res && !ref.is_valid()) {
		
		(*res)->path_cache = String();
		resources.erase(p_path);
		res = nullptr;
	}
	lock.unlock();
	return ref;
}
void ResourceCache::get_cached_resources(List<Ref<Resource>> *p_resources) {