Attempt to access deleted dashboard only displays "Loading..." spinner (no error message shown)

[coffee-squirrel]

Problem description

If a dashboard is deleted and a user attempts to access that dashboard (perhaps she already had the Dashboards page open or has the dashboard saved as a favorite) the page only shows the "Loading..." spinner with no error notification.

Note that this differs slightly from streams, where a red "Could not retrieve Stream" notification appears (although the page is still stuck with the "Loading..." spinner).

Steps to reproduce the problem

1. Log in as an admin
2. Navigate to Dashboards
3. Click the "Create dashboard" button and create a dashboard "Foo"
4. Open a second tab in your browser and navigate to Dashboards, noting that you can see dashboard "Foo"
5. Return to the first tab and select "Delete this dashboard" from the "More actions" menu of dashboard "Foo", confirming you want to delete it
6. Return to the second tab and open your browser's network request monitor
7. Click the link for dashboard "Foo" (e.g. <GRAYLOG_WEB>/dashboards/579fa11c438960168517f09b)
8. Note you see the "Loading..." spinner in the content area
9. Note every second you see a GET request to <GRAYLOG_REST>/dashboards/579fa11c438960168517f09b that returns HTTP 404, and no "Could not retrieve Stream" notification appears

Environment

• Graylog Version: 2.0.3 and 2.1.0-beta.1+1b940e4
• Elasticsearch Version: 2.2.0
• MongoDB Version: 2.6.12
• Operating System: Red Hat Enterprise Linux Server release 6.7
• Browser version: Firefox 47, Chrome 51.0.2704.106m