### 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 (monitor_info->x != monitors[p_screen].x || monitor_info->y != monitors[p_screen].y) { 
					continue;
				}
				if (monitor_info->mode != None) {
					current_mode = monitor_info->mode;
					found_active_mode = true;
					break;
				}
			}
			if (found_active_mode) {
				for (int mode = 0; mode < screen_info->nmode; mode++) {
					XRRModeInfo m_info = screen_info->modes[mode];
					if (m_info.id == current_mode) {
						
						return Math::snapped((float)m_info.dotClock / ((float)m_info.hTotal * (float)m_info.vTotal), 0.01);
					}
				}
			}
			ERR_PRINT("An error occurred while trying to get the screen refresh rate."); 
			return SCREEN_REFRESH_RATE_FALLBACK;
		} else {
			ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
			return SCREEN_REFRESH_RATE_FALLBACK;
		}
	}
	ERR_PRINT("An error occurred while trying to get the screen refresh rate.");
	return SCREEN_REFRESH_RATE_FALLBACK;
}
#ifdef DBUS_ENABLED
void DisplayServerX11::screen_set_keep_on(bool p_enable) {