### 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)

_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	WindowData &wd = windows[p_window];
	int x = 0;
	int y = 0;
	if (!window_get_flag(WINDOW_FLAG_BORDERLESS, p_window)) {
		
		XSync(x11_display, False);
		Atom prop = XInternAtom(x11_display, "_NET_FRAME_EXTENTS", True);
		if (prop != None) {
			Atom type;
			int format;
			unsigned long len;
			unsigned long remaining;
			unsigned char *data = nullptr;
			if (XGetWindowProperty(x11_display, wd.x11_window, prop, 0, 4, False, AnyPropertyType, &type, &format, &len, &remaining, &data) == Success) {
				if (format == 32 && len == 4 && data) {
					long *extents = (long *)data;
					x = extents[0];
					y = extents[2];
				}
				XFree(data);
			}
		}
	}
	XMoveWindow(x11_display, wd.x11_window, p_position.x - x, p_position.y - y);
	_update_real_mouse_position(wd);
}
void DisplayServerX11::window_set_max_size(const Size2i p_size, WindowID p_window) {