Embargo: Group details of example groups can’t be opened

Group details of “embargo-authors-example-group" and "embargo-editors-example-group” can’t be opened. An error is logged:
Caused by: java.lang.IllegalArgumentException: Node name can not be empty.
[INFO] [talledLocalContainer] at org.hippoecm.repository.api.NodeNameCodec.encode(NodeNameCodec.java:133)
[INFO] [talledLocalContainer] at org.hippoecm.repository.api.NodeNameCodec.encode(NodeNameCodec.java:101)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugins.cms.admin.users.User.userExists(User.java:141)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugins.cms.admin.groups.Group.getMembersAsDetachableUsers(Group.java:279)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugins.cms.admin.groups.ViewGroupPanel.<init>(ViewGroupPanel.java:137)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugins.cms.admin.groups.ViewGroupActionLink$1.create(ViewGroupActionLink.java:51)
[INFO] [talledLocalContainer] at org.apache.wicket.extensions.breadcrumb.panel.BreadCrumbPanel.activate(BreadCrumbPanel.java:116)
[INFO] [talledLocalContainer] at org.hippoecm.frontend.plugins.cms.admin.groups.ViewGroupActionLink.onClick(ViewGroupActionLink.java:49)
[INFO] [talledLocalContainer] at org.apache.wicket.ajax.markup.html.AjaxLink$1.onEvent(AjaxLink.java:86)
[INFO] [talledLocalContainer] at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:146)
[INFO] [talledLocalContainer] at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:633)
[INFO] [talledLocalContainer] ... 34 more

Steps to reproduce:
Open admin > groups
Click the “embargo-authors-example-group" or "embargo-editors-example-group”

We fixed it locally by deleting the empty field for the property ‘hipposys:members’ (the plugin added this empty field)