Improve error handling for featured content

[coverbeck]

Bug Report

If the UI fails to fetch the featured content, e.g, because the bucket doesn't exist:

1. A snackbar pops up saying "failed".
2. The featured content block is empty.

Suggestions:

1. Either don't display a snackbar at all, or improve the message to something like "Error fetching featured content"
2. Either remove the Featured Content title, or have some placeholder text reflecting the error condition.

This error condition will probably/hopefully never occur in production, although you never know, so seems low priority off-hand.

┆Issue is synchronized with this Jira Bug ┆fixVersions: Dockstore 2.X ┆friendlyId: DOCK-1174 ┆sprint: Backlog ┆taskType: Bug