Actions selection counter gets cleared when using back button

[Cauê Thenório]

In Admin's change list page, the actions selection counter (e.g. "99 of 100 selected") will be reset/get out of sync if the user leaves the page and then returns via the browser's back button but the rows will continue selected.

Steps to reproduce:

1. Open the admin's change list page
2. Select some rows, e.g. 10 rows
3. The selection counter text will display "99 of X selected"
4. Click on any link to navigate to another page
5. Click the browser's back button
6. The 10 rows will continue selected

What happens:

• The selection counter text will wrongly display "0 of X selected"

What should happen:

• The selection counter text should display "10 of X selected"