### 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)

int height = p2.y - p1.y;
		if (hdc) {
			HBITMAP hbm = CreateCompatibleBitmap(dc, width, height);
			if (hbm) {
				SelectObject(hdc, hbm);
				BitBlt(hdc, 0, 0, width, height, dc, p1.x, p1.y, SRCCOPY);
				BITMAPINFO bmp_info = {};
				bmp_info.bmiHeader.biSize = sizeof(bmp_info.bmiHeader);
				bmp_info.bmiHeader.biWidth = width;
				bmp_info.bmiHeader.biHeight = -height;
				bmp_info.bmiHeader.biPlanes = 1;
				bmp_info.bmiHeader.biBitCount = 32;
				bmp_info.bmiHeader.biCompression = BI_RGB;
				Vector<uint8_t> img_data;
				img_data.resize(width * height * 4);
				GetDIBits(hdc, hbm, 0, height, img_data.ptrw(), &bmp_info, DIB_RGB_COLORS);
				uint8_t *wr = (uint8_t *)img_data.ptrw();
				for (int i = 0; i < width * height; i++) {
					SWAP(wr[i * 4 + 0], wr[i * 4 + 2]);
				}
				img = Image::create_from_data(width, height, false, Image::FORMAT_RGBA8, img_data);
				DeleteObject(hbm);
			}
			DeleteDC(hdc);
		}
		ReleaseDC(NULL, dc);
	}
	return img;
}
float DisplayServerWindows::screen_get_refresh_rate(int p_screen) const {