Contribution list: Filter speakers correctly (#4712)

Do not attempt to match on all ContributionPersonLinks, only on
those marked as a speaker.

Otherwise a contribution with a second, non-speaker author that has
registered will not show up if searching for non-registered speakers.

CHANGES.rst

@@ -16,7 +16,8 @@ Improvements
 Bugfixes
 ^^^^^^^^
 
-- None so far :)
+- Only consider actual speakers in the "has registered speakers" contribution list filter
+  (:pr:`4712`, thanks :user:`bpedersen2`)
 
 Version 2.3.1
 -------------

indico/modules/events/contributions/lists.py

@@ -90,6 +90,7 @@ def _filter_list_entries(self, query, filters):
             registration_join_criteria = db.and_(
                 Registration.event_id == Contribution.event_id,
                 Registration.is_active,
+                ContributionPersonLink.is_speaker,
                 (Registration.user_id == EventPerson.user_id) | (Registration.email == EventPerson.email)
             )
             contrib_query = (db.session.query(Contribution.id)