Unhandled 400 error when typing more than 10 comma-separated ML class search terms

Sentry Issue: ARKINDEX-FRONTEND-J7

Error: Request failed with status code 400
  at call (./js/api.js:74:85)
  at u (None:1:410)
  at a (None:1:410)
  at l/</< (None:1:410)
  at l/< (None:1:410)
...
(36 additional frame(s) were not displayed)

The frontend currently prevents sending over 10 space-separated search terms to the ListCorpusMLClasses API, since we have a limit on search terms. However, Django REST Framework is responsible for the splitting into search terms, and commas are replaced with spaces. When typing something like 1,2,3,4,5,6,7,8,9,0,ohno, the frontend treats it as one search term and sends it to the backend, but the backend sees eleven terms, causes a HTTP 400 and the frontend does not display it or handle it in any way.