message: Skip generatePreview if event is not part of the live timeline
diff: @@ -176,7 +176,7 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
  if (payload.action === 'MatrixActions.Room.timeline' || payload.action === 'MatrixActions.Event.decrypted') {
  const event = payload.event; // TODO: Type out the dispatcher
  - if (!this.previews.has(event.getRoomId())) return; // not important
  + if (!this.previews.has(event.getRoomId()) || !event.isLiveEvent) return; // not important
  await this.generatePreview(this.matrixClient.getRoom(event.getRoomId()), TAG_ANY);
  }
  }
  