message: EventIndex: Don't process checkpoints that don't have a valid token.
  Some rooms might have null as a token, don't add those to be crawled nor
  to the index.
  Catch any other errors that might occur during the addition of an
  initial checkpoint and log them.
diff: @@ -115,10 +115,20 @@ export default class EventIndex extends EventEmitter {
  direction: "f",
  };
  + try {
  + if (backCheckpoint.token) {
  await indexManager.addCrawlerCheckpoint(backCheckpoint);
  - await indexManager.addCrawlerCheckpoint(forwardCheckpoint);
  this.crawlerCheckpoints.push(backCheckpoint);
  + }
  +
  + if (forwardCheckpoint.token) {
  + await indexManager.addCrawlerCheckpoint(forwardCheckpoint);
  this.crawlerCheckpoints.push(forwardCheckpoint);
  + }
  + } catch (e) {
  + console.log("EventIndex: Error adding initial checkpoints for room",
  + room.roomId, backCheckpoint, forwardCheckpoint, e);
  + }
  }));
  }
  