From bb6905bdcdb991687c91b867f0562f6990e3e1c0 Mon Sep 17 00:00:00 2001
From: Bruno Windels <bruno@windels.cloud>
Date: Fri, 4 Jun 2021 16:05:28 +0200
Subject: [PATCH 1/2] don't assume localEntries exists, as load races with
 sync.afterSync

---
 src/matrix/room/timeline/Timeline.js | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/matrix/room/timeline/Timeline.js b/src/matrix/room/timeline/Timeline.js
index eab71255..aa331058 100644
--- a/src/matrix/room/timeline/Timeline.js
+++ b/src/matrix/room/timeline/Timeline.js
@@ -159,7 +159,9 @@ export class Timeline {
         // Once the subscription is setup, MappedList will set up the local
         // relations as needed with _applyAndEmitLocalRelationChange,
         // so we're not missing anything by bailing out.
-        if (!this._localEntries.hasSubscriptions) {
+        //
+        // _localEntries can also not yet exist
+        if (!this._localEntries?.hasSubscriptions) {
             return;
         }
         // find any local relations to this new remote event
@@ -301,4 +303,4 @@ export function tests() {
             assert.equal(Array.from(timeline.entries)[0].isRedacting, true);
         }
     }
-}
\ No newline at end of file
+}

From 7691b28503e4b444b6a6e1dcc5f0037c41a3b105 Mon Sep 17 00:00:00 2001
From: Bruno Windels <bruno@windels.cloud>
Date: Fri, 4 Jun 2021 16:28:08 +0200
Subject: [PATCH 2/2] prevent another race between sync and openTimeline

---
 src/matrix/room/timeline/Timeline.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/matrix/room/timeline/Timeline.js b/src/matrix/room/timeline/Timeline.js
index aa331058..ecba1f2a 100644
--- a/src/matrix/room/timeline/Timeline.js
+++ b/src/matrix/room/timeline/Timeline.js
@@ -32,7 +32,8 @@ export class Timeline {
         this._disposables = new Disposables();
         this._pendingEvents = pendingEvents;
         this._clock = clock;
-        this._remoteEntries = null;
+        // constructing this early avoid some problem while sync and openTimeline race
+        this._remoteEntries = new SortedArray((a, b) => a.compare(b));
         this._ownMember = null;
         this._timelineReader = new TimelineReader({
             roomId: this._roomId,
@@ -96,7 +97,6 @@ export class Timeline {
     }
 
     _setupEntries(timelineEntries) {
-        this._remoteEntries = new SortedArray((a, b) => a.compare(b));
         this._remoteEntries.setManySorted(timelineEntries);
         if (this._pendingEvents) {
             this._localEntries = new MappedList(this._pendingEvents, pe => {