State icons occasionally absent from items in sidebar

The downloaded & favourited state icons are sometimes missing from items in the sidebar. For reproduction, this is most immediately obvious by filtering by one of these factors, & checking a number of entries for the correct icons.

At first glance, I can't say I've seen any consistency or pattern to which items are affected.

**Example**

Current state of item, as shown through shelf UI

Start by reproducing the issue in the macOS sidebar: filter by downloaded or favourited state and compare several entries with the shelf UI shown in the examples. Trace how sidebar items obtain and display these state icons; done means the correct icons appear consistently for every matching item.

Written by the indexing model from the issue text.