There are a few cases, where the result of CrashAnalysis is empty. 

Sample stacktrace.

Generator crash.crash_pipeline.PublishResultPipeline(*(u'fracas', {u'channel': u'dev', u'platform': u'win', u'process_type': u'renderer', u'signature': u'[Renderer hang] content::ResourceDispatchThrottler::ForwardMessage', u'version': u'56.0.2924.3'}), **{})#c07b0d1d412b47aa8085b9fb055853a2 raised exception. KeyError: 'found'
Traceback (most recent call last):
  File "/base/data/home/apps/s~google.com:findit-for-me/crash-backend-fracas:katesonia.397224452994512065/first_party/pipeline_utils/appengine_third_party_pipeline_python_src_pipeline/pipeline.py", line 2158, in evaluate
    self, pipeline_key, root_pipeline_key, caller_output)
  File "/base/data/home/apps/s~google.com:findit-for-me/crash-backend-fracas:katesonia.397224452994512065/first_party/pipeline_utils/appengine_third_party_pipeline_python_src_pipeline/pipeline.py", line 1113, in _run_internal
    return self.run(*self.args, **self.kwargs)
  File "/base/data/home/apps/s~google.com:findit-for-me/crash-backend-fracas:katesonia.397224452994512065/crash/crash_pipeline.py", line 187, in run
    result = analysis.ToPublishableResult(self._crash_identifiers)
  File "/base/data/home/apps/s~google.com:findit-for-me/crash-backend-fracas:katesonia.397224452994512065/model/crash/crash_analysis.py", line 177, in ToPublishableResult
    if result['found'] and 'suspected_cls' in result:
KeyError: 'found'