### Godot version

Godot Engine v4.0.stable.official.92bee43ad

### System information

Windows 10

### Issue description

The documentation states that passing ```null``` into the image parameter of ```set_custom_mouse_cursor``` will change it back to the system cursor, however I find that it removes the cursor's image entirely, rather than setting it to the system's cursor.


### Steps to reproduce

```var isimage = false
var theimage = load("res://final.png")

func _on_my_button_pressed():
    if isimage == false:
        Input.set_custom_mouse_cursor(theimage, Input.CURSOR_ARROW, Vector2(16,16))
        isimage = true
        
    else:
        Input.set_custom_mouse_cursor(null)
        isimage = false```

When the button is pressed, the cursor is meant to change to the new cursor. When it has been pressed a second time, it changes back to the default cursor. However, upon pressing it a second time, it simply disappears. The cursor becomes visible again when the cursor exits and re-enters the window.

### Minimal reproduction project

[null mouse.zip](https://github.com/godotengine/godot/files/10901969/null.mouse.zip)

};
	if (cursors_cache.has(p_shape)) {
		SetCursor(cursors[p_shape]);
	} else {
		SetCursor(LoadCursor(hInstance, win_cursors[p_shape]));
	}
	cursor_shape = p_shape;
}
DisplayServer::CursorShape DisplayServerWindows::cursor_get_shape() const {
	return cursor_shape;
}
void DisplayServerWindows::cursor_set_custom_image(const Ref<Resource> &p_cursor, CursorShape p_shape, const Vector2 &p_hotspot) {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_INDEX(p_shape, CURSOR_MAX);
	if (p_cursor.is_valid()) {
		RBMap<CursorShape, Vector<Variant>>::Element *cursor_c = cursors_cache.find(p_shape);
		if (cursor_c) {
			if (cursor_c->get()[0] == p_cursor && cursor_c->get()[1] == p_hotspot) {
				cursor_set_shape(p_shape);
				return;
			}
			cursors_cache.erase(p_shape);
		}
		Ref<Texture2D> texture = p_cursor;
		ERR_FAIL_COND(!texture.is_valid());
		Ref<AtlasTexture> atlas_texture = p_cursor;
		Size2 texture_size;
		Rect2 atlas_rect;
		if (atlas_texture.is_valid()) {
			texture = atlas_texture->get_atlas();