Fix metadata fields not editable during multi edit

[Arnei]

In the modal for editing multiple events at the same time, the fields "presenter(s)" and "contributor(s)" were not editable in some cases. This patch fixes that.

How to test this

This patch should ideally be tested with a production Opencast. Unfortunately, I do not actually know what the exact Opencast configuration is that causes the error this patch this is supposed to fix. The modal for editing multiple events can be found in the events table next to the search bar and filters.

[github-actions]

Use docker or podman to test this pull request locally.

Run test server using develop.opencast.org as backend:

podman run --rm -it -p 127.0.0.1:3000:3000 ghcr.io/opencast/opencast-admin-interface:pr-1041

Specify a different backend like stable.opencast.org:

podman run --rm -it -p 127.0.0.1:3000:3000 -e PROXY_TARGET=https://stable.opencast.org ghcr.io/opencast/opencast-admin-interface:pr-1041

It may take a few seconds for the interface to spin up.
It will then be available at http://127.0.0.1:3000.
For more options you can pass on to the proxy, take a look at the README.md.

[github-actions]

This pull request is deployed at test.admin-interface.opencast.org/1041/2025-01-03_14-31-13/ .
It might take a few minutes for it to become available.