Steps to reproduce:
a) Create a user "alice".
b) Create a group "employee" with a dynamic user assignment (username == alice).
c) Verify that alice is a dynamic member of the group "employee".
d) Now edit "employee" and "-" the search condition for dynamic user assignment and click finish.
e) The condition is not deleted as expected, alice is still a member of the group. Edit the group again and the dynamic user condition search is still in place.