[Findit] Fix a bug that MonitorTryJobPipeline still runs when no try job scheduled.

appengine/findit/waterfall/identify_try_job_culprit_pipeline.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from collections import defaultdict
 import logging
 
 from google.appengine.ext import ndb
 
 from common.git_repository import GitRepository
@@ skipping 260 matching lines @@
 
   # Arguments number differs from overridden method - pylint: disable=W0221
   def run(
       self, master_name, builder_name, build_number, blame_list, try_job_type,
       try_job_id, result):
     """Identifies the information for failed revisions.
 
     Please refer to try_job_result_format.md for format check.
     """
     culprits = None
-    if result and result.get('report'):
+    if try_job_id and result and result.get('report'):
       try_job_data = WfTryJobData.Get(try_job_id)
       if try_job_type == failure_type.COMPILE:
         # For compile failures, the try job will stop if one revision fails, so
         # the culprit will be the last revision in the result.
         failed_revision = _GetFailedRevisionFromCompileResult(result)
         failed_revisions = [failed_revision] if failed_revision else []
         culprits = self._GetCulpritInfo(failed_revisions)
         if culprits:
           result['culprit'] = {
               'compile': culprits[failed_revision]
@@ skipping 41 matching lines @@
         analysis.result_status = updated_result_status
         analysis.suspected_cls = updated_suspected_cls
         analysis.put()
 
     # Store try-job results.
     UpdateTryJobResult()
     # Add try-job results to WfAnalysis.
     UpdateWfAnalysisWithTryJobResult()
 
     _NotifyCulprits(master_name, builder_name, build_number, culprits)
-    return result.get('culprit') if result else None
+    return result.get('culprit') if result else None