### 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)

}
			}
		} else if (image->bits_per_pixel == 24 && image->red_mask == 0x0000ff && image->green_mask == 0x00ff00 && image->blue_mask == 0xff0000) {
			for (int y = 0; y < height; y++) {
				for (int x = 0; x < width; x++) {
					wr[(y * width + x) * 4 + 0] = sr[(y * width + x) * 3 + 2];
					wr[(y * width + x) * 4 + 1] = sr[(y * width + x) * 3 + 1];
					wr[(y * width + x) * 4 + 2] = sr[(y * width + x) * 3 + 0];
					wr[(y * width + x) * 4 + 3] = 255;
				}
			}
		} else if (image->bits_per_pixel == 32 && image->red_mask == 0xff0000 && image->green_mask == 0x00ff00 && image->blue_mask == 0x0000ff) {
			for (int y = 0; y < height; y++) {
				for (int x = 0; x < width; x++) {
					wr[(y * width + x) * 4 + 0] = sr[(y * width + x) * 4 + 2];
					wr[(y * width + x) * 4 + 1] = sr[(y * width + x) * 4 + 1];
					wr[(y * width + x) * 4 + 2] = sr[(y * width + x) * 4 + 0];
					wr[(y * width + x) * 4 + 3] = 255;
				}
			}
		} else {
			XFree(image);
			ERR_FAIL_V_MSG(Ref<Image>(), vformat("XImage with RGB mask %x %x %x and depth %d is not supported.", (uint64_t)image->red_mask, (uint64_t)image->green_mask, (uint64_t)image->blue_mask, (int64_t)image->bits_per_pixel));
		}
		img = Image::create_from_data(width, height, false, Image::FORMAT_RGBA8, img_data);
		XFree(image);
	}
	return img;
}
float DisplayServerX11::screen_get_refresh_rate(int p_screen) const {