### 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)

}
	return ret.substr(0, 2);
}
String DisplayServerX11::keyboard_get_layout_name(int p_index) const {
	String ret;
	XkbDescRec *kbd = XkbAllocKeyboard();
	if (kbd) {
		kbd->dpy = x11_display;
		XkbGetControls(x11_display, XkbAllControlsMask, kbd);
		XkbGetNames(x11_display, XkbSymbolsNameMask, kbd);
		XkbGetNames(x11_display, XkbGroupNamesMask, kbd);
		int _group_count = 0;
		const Atom *groups = kbd->names->groups;
		if (kbd->ctrls != nullptr) {
			_group_count = kbd->ctrls->num_groups;
		} else {
			while (_group_count < XkbNumKbdGroups && groups[_group_count] != None) {
				_group_count++;
			}
		}
		if (p_index >= 0 && p_index < _group_count) {
			ret = get_atom_name(x11_display, groups[p_index]);
		} else {
			ERR_PRINT("Index " + itos(p_index) + "is out of bounds (" + itos(_group_count) + ").");
		}
		XkbFreeKeyboard(kbd, 0, true);
	}
	return ret;
}
Key DisplayServerX11::keyboard_get_keycode_from_physical(Key p_keycode) const {