Describe the bug
As outlined in
#6436 (comment) :

The reimport of metadata does currently not work correctly if metadata groups in the editor contain empty fields. In that case the same group from the catalogue is duplicated.

To Reproduce
Steps to reproduce the behavior:

1. Have metadata groups with empty fields (e.g. a person's role) in the metadata of the current document
2. Reimport the metadata from the catalogue
3. Metadata Groups with empty fields are duplicated

Expected behavior

The reimport should also work for metadata groups with empty fields.

Possible fix
see: #6436 (comment)

Release
Kitodo 3.8.x, master