### 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_INDEX(p_shape, CURSOR_MAX);
	if (cursor_shape == p_shape) {
		return;
	}
	if (mouse_mode != MOUSE_MODE_VISIBLE && mouse_mode != MOUSE_MODE_CONFINED) {
		cursor_shape = p_shape;
		return;
	}
	static const LPCTSTR win_cursors[CURSOR_MAX] = {
		IDC_ARROW,
		IDC_IBEAM,
		IDC_HAND, 
		IDC_CROSS,
		IDC_WAIT,
		IDC_APPSTARTING,
		IDC_SIZEALL,
		IDC_ARROW,
		IDC_NO,
		IDC_SIZENS,
		IDC_SIZEWE,
		IDC_SIZENESW,
		IDC_SIZENWSE,
		IDC_SIZEALL,
		IDC_SIZENS,
		IDC_SIZEWE,
		IDC_HELP