Stop trying to fetch events with event_id=None. (#5753)

`None` is not a valid event id, so queuing up a database fetch for it seems
like a silly thing to do.

I considered making `get_event` return `None` if `event_id is None`, but then
its interaction with `allow_none` seemed uninituitive, and strong typing ftw.

1 files changed, 4 insertions, 1 deletions

diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py

index 44441957db..83fe4764d8 100644
--- a/synapse/storage/events_worker.py
+++ b/synapse/storage/events_worker.py
@@ -139,8 +139,11 @@ class EventsWorkerStore(SQLBaseStore):
                 If there is a mismatch, behave as per allow_none.
 
         Returns:
-            Deferred : A FrozenEvent.
+            Deferred[EventBase|None]
         """
+        if not isinstance(event_id, str):
+            raise TypeError("Invalid event event_id %r" % (event_id,))
+
         events = yield self.get_events_as_list(
             [event_id],
             check_redacted=check_redacted,