Don't include None's in _get_events_txn

synapse/storage/_base.py

@@ -446,7 +446,7 @@ class SQLBaseStore(object):
         if not event_ids:
             return []
 
-        return [
+        events = [
             self._get_event_txn(
                 txn, event_id,
                 check_redacted=check_redacted,
@@ -455,6 +455,8 @@ class SQLBaseStore(object):
             for event_id in event_ids
         ]
 
+        return [e for e in events if e]
+
     def _get_event_txn(self, txn, event_id, check_redacted=True,
                        get_prev_content=False):
         sql = (