TypeError: can't convert undefined to object

The issue was observed when entering some text in the search field for which no results were found.

https://sentry.amiv.ethz.ch/amiv/website/issues/2257/

TypeError: can't convert undefined to object
  at reducer (./src/store/studydocuments/reducer.js:144:16)
  at dispatchNext (./src/store/apiMiddleware.js:48:7)
  at h/</</< (./src/store/apiMiddleware.js:88:7)
...
(1 additional frame(s) were not displayed)