### 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 (keycode == Key::NONE) {
		keycode = (Key)physical_keycode;
	}
	
	
	
	
	
	Ref<InputEventKey> k;
	k.instantiate();
	k->set_window_id(p_window);
	_get_key_modifier_state(xkeyevent->state, k);
	
	
	
	
	
	if (xkeyevent->type != KeyPress) {
		p_echo = false;
		
		
		if (p_event_index + 1 < p_events.size()) {
			XEvent &peek_event = p_events[p_event_index + 1];
			
			
			
			
			
#define ABSDIFF(x, y) (((x) < (y)) ? ((y) - (x)) : ((x) - (y)))