Only try to compute running_all_jobs time if we know when try-job verifier started

appengine/chromium_cq_status/handlers/patch_summary.py

 # Copyright 2014 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 datetime import datetime
 from itertools import chain
 import logging
 
 import webapp2
 
@@ skipping 83 matching lines @@
     timestamp = to_unix_timestamp(record.timestamp)
     if last_patch_action:
       patch_state_duration = timestamp - last_patch_timestamp
 
     # Verifier job updates.
     if verifier == TRYJOBVERIFIER:
       if action == 'verifier_start':
         verifier_start_timestamp = timestamp
       elif action == 'verifier_jobs_update':
         job_tracker.update_jobs(record)
-      elif action in ('verifier_pass', 'verifier_fail'):
+      elif (action in ('verifier_pass', 'verifier_fail') and
+            verifier_start_timestamp is not None):
         durations['running_all_jobs'] = timestamp - verifier_start_timestamp
         verifier_start_timestamp = None
 
     # Patch state updates.
     if action and action.startswith('patch_'):
       if last_patch_action == 'patch_throttled':
         durations['blocked_on_throttled_tree'] += patch_state_duration
       if last_patch_action == 'patch_tree_closed':
         durations['blocked_on_closed_tree'] += patch_state_duration
     if action == 'patch_committed':
@@ skipping 160 matching lines @@
     return min(iterable)
   except ValueError:  # pragma: no cover
     return None
 
 
 def maybe_max(iterable):
   try:
     return max(iterable)
   except ValueError:  # pragma: no cover
     return None