### 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)

}
			
			Vector<long> pd;
			pd.resize(2 + w * h);
			pd.write[0] = w;
			pd.write[1] = h;
			const uint8_t *r = img->get_data().ptr();
			long *wr = &pd.write[2];
			uint8_t const *pr = r;
			for (int i = 0; i < w * h; i++) {
				long v = 0;
				
				v |= pr[3] << 24 | pr[0] << 16 | pr[1] << 8 | pr[2];
				*wr++ = v;
				pr += 4;
			}
			if (net_wm_icon != None) {
				XChangeProperty(x11_display, wd.x11_window, net_wm_icon, XA_CARDINAL, 32, PropModeReplace, (unsigned char *)pd.ptr(), pd.size());
			}
			if (!g_set_icon_error) {
				break;
			}
		}
	} else {
		XDeleteProperty(x11_display, wd.x11_window, net_wm_icon);
	}
	XFlush(x11_display);
	XSetErrorHandler(oldHandler);
}
void DisplayServerX11::window_set_vsync_mode(DisplayServer::VSyncMode p_vsync_mode, WindowID p_window) {