Editing series categories and labels is broken in `next`

# Steps to reproduce:

- Create a series in Opencast and upload two videos into it
- Open one of them in the annotation tool and create a series category
- Open the second video and try to edit the series category (e.g. the title)
  - This works, but the label is duplicated until the next refresh
- Try to edit an existing label and see that it just doesn't have any effect