V6 Tutorial crashes after deleting an invoice and then hitting browser's back button

[bmm-brobbins]

Referring to this getting-started tutorial (also on Stackblitz here).

After deleting an invoice and then hitting the browser's back button, the Invoice component fails because it's trying to retrieve a no-longer-existing invoice. No complaints, rather this is a good example for my question:

How can we properly restore an app's previous state, or an applicable subset of state, for this type of situation, where the user has clicked the browser's back button?

I realize that the URL itself can be made to contain some variables that can be considered "state". But what about large or complex state variables? How can we restore these to their rightful values as the user performs back and forward browser navigation?

Thank you.