Data Routing: Insensitive toggles and error on Destinations page

When on the Destinations Data Routing page, the toggle options for Index Set and Outputs seem to not work when clicked. There is no sign of progress or error when clicking them. Nothing seems to happen.

I also noticed the following error a while after the page loaded. It takes about 5 seconds to appear.

```
Loading index set with id: 6617f27053ebc348bd321744 failed with status: FetchError: There was an error fetching a resource: . Additional information: Cannot invoke "org.joda.time.Period.toStandardDuration()" because the return value of "org.graylog.plugins.datatiering.hotwarm.HotWarmDataTieringConfig.indexHotLifetimeMin()" is null
```