Make `prev_state` field optional

The `prev_state` field on events is not specced and so synapse shouldn't
explode if an event is missing the field.

Fixes #4787

1 files changed, 0 insertions, 1 deletions

diff --git a/synapse/events/__init__.py b/synapse/events/__init__.py

index bd130f8816..fafa135182 100644
--- a/synapse/events/__init__.py
+++ b/synapse/events/__init__.py
@@ -141,7 +141,6 @@ class EventBase(object):
     origin = _event_dict_property("origin")
     origin_server_ts = _event_dict_property("origin_server_ts")
     prev_events = _event_dict_property("prev_events")
-    prev_state = _event_dict_property("prev_state")
     redacts = _event_dict_property("redacts")
     room_id = _event_dict_property("room_id")
     sender = _event_dict_property("sender")