### 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)

atlas_rect.size.width = texture->get_width();
			atlas_rect.size.height = texture->get_height();
			atlas_rect.position.x = atlas_texture->get_region().position.x;
			atlas_rect.position.y = atlas_texture->get_region().position.y;
			texture_size.width = atlas_texture->get_region().size.x;
			texture_size.height = atlas_texture->get_region().size.y;
		} else {
			texture_size.width = texture->get_width();
			texture_size.height = texture->get_height();
		}
		ERR_FAIL_COND(p_hotspot.x < 0 || p_hotspot.y < 0);
		ERR_FAIL_COND(texture_size.width > 256 || texture_size.height > 256);
		ERR_FAIL_COND(p_hotspot.x > texture_size.width || p_hotspot.y > texture_size.height);
		Ref<Image> image = texture->get_image();
		ERR_FAIL_COND(!image.is_valid());
		if (image->is_compressed()) {
			image = image->duplicate(true);
			Error err = image->decompress();
			ERR_FAIL_COND_MSG(err != OK, "Couldn't decompress VRAM-compressed custom mouse cursor image. Switch to a lossless compression mode in the Import dock.");
		}
		UINT image_size = texture_size.width * texture_size.height;
		
		COLORREF *buffer = nullptr;
		BITMAPV5HEADER bi;
		ZeroMemory(&bi, sizeof(bi));
		bi.bV5Size = sizeof(bi);
		bi.bV5Width = texture_size.width;
		bi.bV5Height = -texture_size.height;
		bi.bV5Planes = 1;
		bi.bV5BitCount = 32;