bug: not possible to select "serbian"

[carlinmack]

Describe the bug

When selecting the language in the additional description section (and possibly also title), it is impossible to choose Serbian. There is an offer for Serbo-Croatian and Romano-Serbian. However when a space is put after Serbian and then removed, Serbian appears but quickly disappears.

The main languages field works correctly

Serbian does appear to be in languages.yaml

How to reproduce

1. Open the deposit form
2. Add an additional description
3. Search a language, e.g. "Dutch"

Result:

Here is the network tab and the request that fetched the languages from the back end:

It seems that the backend fetches multiple languages but only one is displayed