message: Handle null user IDs
diff: @@ -21,13 +21,14 @@ export class MetricsLambda implements IPartitionLambda {
  // Update and retrieve the minimum sequence number
  const message = baseMessage as core.IRawOperationMessage;
  + const userId = message.user && message.user.id ? message.user.id : "anonymous";
  const event = new aria.AWTEventProperties();
  event.setName(this.eventName);
  event.setTimestamp(message.timestamp);
  event.setProperty("tenantId", message.tenantId, aria.AWTPropertyType.String);
  event.setProperty("documentId", message.documentId, aria.AWTPropertyType.String);
  - event.setProperty("userId", message.user.id, aria.AWTPropertyType.String);
  + event.setProperty("userId", userId, aria.AWTPropertyType.String);
  event.setProperty("environment", this.environment, aria.AWTPropertyType.String);
  event.setProperty("clientId", message.clientId, aria.AWTPropertyType.String);
  this.logger.logEvent(event);
  