During creation of the custom data type entry, it can reference to it self. We should prevent user from selecting the newly added entry[1] or currently editing entry [2].

[1]

[2]

Acceptance test

1. Create DMN
2. Change to "Data Types"
3. Add new one
4. Change name and click on "Save"
5. Try edit again and now if issue still exist you can see name of Data Type in "Custom" area