**Steps to reproduce**

* Create a Begin of the deletion category
* Create aEnd of the deletion work package and Begin of the insertiondo notEnd of the insertion assign Begin of the insertionaEnd of the insertion Begin of the deletion theEnd of the deletion category
* Begin of the deletion Delete the category
* End of the deletion Go to the overview page and select the widget to display by category Begin of the insertion
* The same happens for assignees

**Notes**

The bug also affects the work package table when grouping by category or assignee (or any other associated resource) and having a group without a value.End of the insertion