public void PopPage()
{
_ = PageStack ??
throw new NullReferenceException("Can't go back a page when there are no pages in the stack");
_ = (PageStack.Count <= 0) ?
throw new IndexOutOfRangeException("Can't go back a page when there are no pages in the stack") : 0;
_ = (PageStackIndex - 1 < 0) ?
throw new IndexOutOfRangeException("Can't go back a page while being on the first page") : 0;
DestroyPage();
PageStack.RemoveAt(PageStackIndex);
currentPage = PageStack[PageStackIndex - 1];
PageStackIndex = PageStack.Count - 1;
ShowPage();
}