Fix a minor issue in Nuance which could cause the trigger daemon to poll too often

Summary: Ref T10537. Currently, when you have at least two cursors, the daemon can poll too frequently when processing the last source because it never hits the end-of-list condition.

Test Plan:
  - Ran `bin/phd debug trigger`.
  - Observed huge volumes of output before change as triggers fired as fast as possible.
  - Observed reasonable poll frequency after change.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10537

Differential Revision: https://secure.phabricator.com/D15464

src/infrastructure/daemon/workers/PhabricatorTriggerDaemon.php

@@ -411,7 +411,7 @@ final class PhabricatorTriggerDaemon
     }
 
     // If we haven't loaded sources yet, load them first.
-    if (!$this->nuanceSources) {
+    if (!$this->nuanceSources && !$this->nuanceCursors) {
       $this->anyNuanceData = false;
 
       $sources = id(new NuanceSourceQuery())