Vues :

While deleting a field, you receive an "Object Reference....." error where part of the error contains this text:

In DocuWare Administration > File Cabinet > Options > Links, check the defined links.
In the links, you have the option to see the search-dialog of the link. The problem is that there are likely to be some  link configurations where the search criteria is missing. As soon as you enter valid search criteria the error message will disappear.