This is crashing on chromium.swarm

2017-03-07 18:38:24-0800 [HTTPPageGetter,client] Unhandled error in Deferred:
2017-03-07 18:38:24-0800 [HTTPPageGetter,client] Unhandled Error
        Traceback (most recent call last):
          File "/home/chrome-bot/buildbot/build/third_party/twisted_10_2/twisted/internet/defer.py", line 1141, in unwindGenerator
            return _inlineCallbacks(None, f(*args, **kwargs), Deferred())
          File "/home/chrome-bot/buildbot/build/third_party/twisted_10_2/twisted/internet/defer.py", line 1020, in _inlineCallbacks
            result = g.send(result)
          File "/home/chrome-bot/buildbot/build/scripts/master/pubsub_json_status_push.py", line 216, in _stop
            # Cache pending builds by brid, because they are expensive to query.
          File "/home/chrome-bot/buildbot/build/third_party/twisted_10_2/twisted/internet/defer.py", line 1141, in unwindGenerator
            return _inlineCallbacks(None, f(*args, **kwargs), Deferred())
        --- <exception caught here> ---
          File "/home/chrome-bot/buildbot/build/third_party/twisted_10_2/twisted/internet/defer.py", line 1020, in _inlineCallbacks
            result = g.send(result)
          File "/home/chrome-bot/buildbot/build/scripts/master/pubsub_json_status_push.py", line 281, in _doStatusPush
            # that.  Making this 9MB to account for potential overhead.
          File "/home/chrome-bot/buildbot/build/scripts/master/pubsub_json_status_push.py", line 386, in _loadBuild
            self._clearPushTimer()
        exceptions.AttributeError: 'NoneType' object has no attribute 'asDict'