TypeErrors when deleting the main displayed element using the details panel delete button

Sentry Issues: ARKINDEX-FRONTEND-AFY (on a folder element), ARKINDEX-FRONTEND-AFZ (on an element with a polygon)

TypeError: t.reduce is not a function
  at call (./js/store/corpora.js:28:8)
  at call (./js/store/corpora.js:113:30)
  at p (None:117:3)
  at s (None:117:3)
...
(9 additional frame(s) were not displayed)

1. Open any element
2. In the details panel, click the red trash button
3. Click Delete in the modal
4. Boom