Fix message load in Thread list (#7124)

src/components/views/rooms/EventTile.tsx

@@ -1165,12 +1165,15 @@ export default class EventTile extends React.Component<IProps, IState> {
             || this.state.hover
             || this.state.actionBarFocused);
 
+        const room = MatrixClientPeg.get().getRoom(this.props.mxEvent.getRoomId());
+        const thread = room.findThreadForEvent?.(this.props.mxEvent);
+
         // Thread panel shows the timestamp of the last reply in that thread
         const ts = this.props.tileShape !== TileShape.ThreadPanel
             ? this.props.mxEvent.getTs()
-            : this.props.mxEvent.getThread().lastReply.getTs();
+            : thread?.lastReply.getTs();
 
-        const timestamp = showTimestamp ?
+        const timestamp = showTimestamp && ts ?
             <MessageTimestamp
                 showRelative={this.props.tileShape === TileShape.ThreadPanel}
                 showTwelveHour={this.props.isTwelveHour}