Scraper: make sure show times are fetched if details fail

[danielschenk]

For each of the 4 days, the schedule is fetched first, and subsequently, all act pages are fetched to get descriptions. If one of these fail (eg. due to a bad connection or HTML parsing error) the rest of the days' schedules are not fetched anymore in that cycle.

As show times are a critical part of the system, make sure that an error in getting details doesn't stop updating the show times alone.