### 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)

window_set_transient(p_id, INVALID_WINDOW_ID);
	}
#ifdef VULKAN_ENABLED
	if (context_vulkan) {
		context_vulkan->window_destroy(p_id);
	}
#endif
#ifdef GLES3_ENABLED
	if (gl_manager) {
		gl_manager->window_destroy(p_id);
	}
#endif
	if (wd.xic) {
		XDestroyIC(wd.xic);
		wd.xic = nullptr;
	}
	XDestroyWindow(x11_display, wd.x11_xim_window);
#ifdef XKB_ENABLED
	if (xkb_loaded_v05p) {
		if (wd.xkb_state) {
			xkb_compose_state_unref(wd.xkb_state);
			wd.xkb_state = nullptr;
		}
	}
#endif
	XUnmapWindow(x11_display, wd.x11_window);
	XDestroyWindow(x11_display, wd.x11_window);
	windows.erase(p_id);
}
int64_t DisplayServerX11::window_get_native_handle(HandleType p_handle_type, WindowID p_window) const {