fix error (When part of conversation has already been deleted.) (#5216)

diff --git a/app/javascript/mastodon/actions/timelines.js b/app/javascript/mastodon/actions/timelines.js
index cdaafd89c648fd8baadfb830af3a3453d7fa6548..09abe2702a5f5bfe18596f46123e31c9b81d7785 100644 (file)
--- a/app/javascript/mastodon/actions/timelines.js
+++ b/app/javascript/mastodon/actions/timelines.js
@@ -37,7 +37,7 @@ export function updateTimeline(timeline, status) {
     if (status.in_reply_to_id) {
       let parent = getState().getIn(['statuses', status.in_reply_to_id]);
 
-      while (parent.get('in_reply_to_id')) {
+      while (parent && parent.get('in_reply_to_id')) {
         parents.push(parent.get('id'));
         parent = getState().getIn(['statuses', parent.get('in_reply_to_id')]);
       }