Add an error handler for modules whose collections fail to fetch

Instead of potentially crashing out or rendering no-data everywhere, if a modules collection actually fails, then stop rendering and display an error message.

Example at http://localhost:3057/performance/site-activity-deputy-prime-ministers-office on master at the moment.

Should probably test against this message being present in cheapseats too, since backdrop *error*s (as opposed to empty data-sets) should cause a fail condition for published dashboards.