TypeError when loading the dataset details view

Sentry Issue: ARKINDEX-FRONTEND-BZ6

TypeError: n is undefined
  at selectSet (/arkindex/1.7.1/arkindex-users-1.7.1.js:1:1591845)
  at dataset (/arkindex/1.7.1/arkindex-users-1.7.1.js:1:1592722)
  at i (/arkindex/1.7.1/arkindex-vendors-1.7.1.js:1:85088)
  at s (/arkindex/1.7.1/arkindex-vendors-1.7.1.js:1:85172)
  at v (/arkindex/1.7.1/arkindex-vendors-1.7.1.js:1:90757)
...
(13 additional frame(s) were not displayed)

The dataset details view selects the first set of the dataset automatically using a watcher on dataset, but dataset may be undefined when the dataset has not yeen been loaded. Because of Vue reactivity shenanigans, the watcher may be triggered while the value is undefined, but it does not include a null check.