Uninstalling an app with installed Add-ons doesn't update the Add-ons GUI

Submitted by kri..@..il.com

Link to original bug (#792561)

Description

Steps to reproduce:

1. Use Software to install an app that provides add-ons, like Pidgin.
2. Install some of the app's add-ons.
3. Uninstall the app.

Actual results: The app and its add-ons get uninstalled, but the details page for the app still says "Installed" next to the add-ons that were installed, and their checkboxes remain checked. Unchecking/re-checking the boxes doesn't trigger anything, and behaves just like clicking the checkboxes for an uninstalled app's add-ons.

Expected results: All of the app's add-ons should no longer appear to be installed: their checkboxes should be made blank, and "Installed" should not appear next to them.