### 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 (drop_events) {
		if (user_proc) {
			return CallWindowProcW(user_proc, hWnd, uMsg, wParam, lParam);
		} else {
			return DefWindowProcW(hWnd, uMsg, wParam, lParam);
		}
	}
	WindowID window_id = INVALID_WINDOW_ID;
	bool window_created = false;
	
	
	
	for (const KeyValue<WindowID, WindowData> &E : windows) {
		if (E.value.hWnd == hWnd) {
			window_id = E.key;
			window_created = true;
			break;
		}
	}
	
	
	
	if (!window_created) {
		
		return _handle_early_window_message(hWnd, uMsg, wParam, lParam);
	}
	
	switch (uMsg) {
		case WM_NCHITTEST: {