Addon store: Handle lost selection when filtering (#14777)
Part of #13985
Summary of the issue:
When an add-on is selected in the add-on store, information is displayed.
An index is kept to show the current selection, even when filtering add-ons.
When filtering add-ons, add-ons may disappear from the list, meaning an add-on at that index can no longer be selected.
This causes an error to be logged when the current selected index is no longer available after filtering add-ons
Description of user facing changes
No errors being spammed to console, no lag when filtering add-ons while an add-on is currently selected.
Description of development approach
Handle the case where the current selected index is lost
