Unhandled HTTP 400 error when creating a transcription on an element without a zone

Sentry Issue: ARKINDEX-FRONTEND-BC

Error: Request failed with status code 400
  at createError (./node_modules/axios/lib/core/createError.js:16:15)
  at settle (./node_modules/axios/lib/core/settle.js:17:12)
  at apply (./node_modules/axios/lib/adapters/xhr.js:61:7)
  at r (./node_modules/@sentry/browser/esm/helpers.js:71:23)

1. Open any element without a zone, such as a folder
2. Open the children tree
3. Click on the A+ icon to add a transcription
4. Type anything and submit
5. Profit

• The frontend should not allow creating transcriptions on elements without zones
• Errors are not properly handled although they are displayed (either an extraneous throw in the store, or a missing catch)