quiz answer dashboard does not load if never visited

[jkolsen]

When using an answer dashboard from a quiz activity as a dashboard, it is blank if that dashboard was never visited by the instructor during the quiz activity as a dashboard.

To recreate:

1. have a quiz activity followed by a dashboard activity for that answers of that quiz
2. Have the students answer the quiz with the instructor never looking at the dashboard
3. go to the next activity (dashboard activity)