New accounts on new IdP without any identifyable attributes get ghost account

[dnmvisser]

User logs in from unknown IdP.
IdP entityID gets added, default identifyable attributes get inserted.
IdP does not send any of them, so login should fail with message "service needs at least one of ... etc", but instead user is given a valid ID:

Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: === BEGIN ===
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: entityid does not exist, adding it
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: adding default id attributes for entityid_id: 179
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: entityid does not exist, adding account
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting attributes
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting eduPersonEntitlement => 'urn:mace:dir:entitlement:common-lib-terms'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting eduPersonScopedAffiliation => 'member@dfn.de'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting eduPersonScopedAffiliation => 'student@dfn.de'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting fname => 'first_name'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting lname => 'last_name'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting fullname => 'first_name last_name'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting idpname => 'German National Research and Education Network, DFN'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting organisation => 'German National Research and Education Network, DFN'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting email => 'invalid_email_needs_updating'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Inserting country => '0'
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: Returning user_id 1635
Aug 15 15:29:23 simplesamlphp.wayf DEBUG [84eaa19fb8] AccountLinker: === END ===

Looks like some issues with rare combination of new idp, new user, and no proper attributes.