Angular 2中着陆页上的动态反向链接

I have a item page built in Angular 2 that is linked from an items list page. I am trying to add a 'back' link which takes the user back to the items list page restoring the previous URL with route params. That works fine with Location.back(). However, if a user lands on the items page via a deep link, there is no history in the Location object, so the Location.back() doesn't work. I tried the following, so if the back() function doesn't work, the app triggers the navigate() function, but it throws an error once the app navigates back to the items page:I have a item page built in Angular 2 that is l