Command line I am trying to run locally to test for possible smoothness regressions

python tools\perf\run_benchmark --browser=release smoothness.top_25_smooth

I am running this on my Windows 10 dev workstation from Chromium source tree.
This used to work before but now I get an error at the end after finishing running all tests, when formatting the report page.

Traceback (most recent call last):
  <module> at D:\src\chrome\src\tools\perf\run_benchmark:22
    sys.exit(main())
  main at D:\src\chrome\src\tools\perf\run_benchmark:19
    return benchmark_runner.main(config, [trybot_command.Trybot])
  main at D:\src\chrome\src\third_party\catapult\telemetry\telemetry\benchmark_runner.py:432
    return command_instance.Run(options)
  Run at D:\src\chrome\src\third_party\catapult\telemetry\telemetry\benchmark_runner.py:245
    return min(255, self._benchmark().Run(args))
  Run at D:\src\chrome\src\third_party\catapult\telemetry\telemetry\benchmark.py:91
    return story_runner.RunBenchmark(self, finder_options)
  RunBenchmark at D:\src\chrome\src\third_party\catapult\telemetry\telemetry\internal\story_runner.py:357
    results.PrintSummary()
  PrintSummary at D:\src\chrome\src\third_party\catapult\telemetry\telemetry\internal\results\page_test_results.py:370
    output_formatter.Format(self)
  Format at D:\src\chrome\src\third_party\catapult\telemetry\telemetry\internal\results\html2_output_formatter.py:25
    histograms = page_test_results.AsHistogramDicts(self._metadata)
  AsHistogramDicts at D:\src\chrome\src\third_party\catapult\telemetry\telemetry\internal\results\page_test_results.py:190
    vinn_result = convert_chart_json.ConvertChartJson(chart_json_path)
  ConvertChartJson at D:\src\chrome\src\third_party\catapult\tracing\tracing\value\convert_chart_json.py:24
    js_args=[os.path.abspath(chart_json)])
  RunFile at D:\src\chrome\src\third_party\catapult\third_party\vinn\vinn\_vinn.py:186
    return _RunFileWithD8(temp_boostrap_file, js_args, v8_args, stdout, stdin)
  _RunFileWithD8 at D:\src\chrome\src\third_party\catapult\third_party\vinn\vinn\_vinn.py:265
    'Exception raised when executing %s:\n%s' % (js_file_path, out))
RuntimeError: Exception raised when executing d:\src\tmp\tmpbqkdwf\_tmp_boostrap.js:
/tracing/value/chart_json_converter.html:54: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of null
            for (var sample of value.values) {
                                    ^
TypeError: Cannot read property 'Symbol(Symbol.iterator)' of null
    at Object.tr.b.iterItems (/tracing/value/chart_json_converter.html:54:37)
    at Object.iterItems (/tracing/base/iteration_helpers.html:173:10)
    at Object.tr.b.iterItems (/tracing/value/chart_json_converter.html:26:14)
    at Object.iterItems (/tracing/base/iteration_helpers.html:173:10)
    at Function.convertChartJson (/tracing/value/chart_json_converter.html:23:12)
    at eval (D:\src\chrome\src\third_party\catapult\tracing\tracing\value\convert_chart_json_cmdline.html:17:27)
    at Object.loadHTMLFile (D:\src\chrome\src\third_party\catapult\third_party\vinn\vinn\html_imports_loader.js:140:5)
    at D:\src\chrome\src\third_party\catapult\third_party\vinn\vinn\d8_bootstrap.js:150:19

Locals:
  _            : None
  args         : ['D:\\src\\chrome\\src\\third_party\\catapult\\third_party\\vinn\\third_party\\v8\\win\\AMD64\\d8.exe', 'd:\\src\\tmp\\tmpbqkdwf\\_tmp_boostrap.js', '--js_arguments', 'D:\\src\\chrome\\src\\third_party\\catapult\\third_party\\vinn\\third_party\\v8\\win\\AMD64\\d8.exe', 'd:\\src\\tmp\\tmpokbk7q']
  full_js_args : ['D:\\src\\chrome\\src\\third_party\\catapult\\third_party\\vinn\\third_party\\v8\\win\\AMD64\\d8.exe', 'd:\\src\\tmp\\tmpokbk7q']
  js_args      : ['d:\\src\\tmp\\tmpokbk7q']
  js_file_path : 'd:\\src\\tmp\\tmpbqkdwf\\_tmp_boostrap.js'
  out          : "/tracing/value/chart_json_converter.html:54: TypeError: Cannot read property 'Symbol(Symbol.iterator)' of null\n            for (var sample of value.values) {\n                                    ^\nTypeError: Cannot read property 'Symbol(Symbol.iterator)' of null\n    at Object.tr.b.iterItems (/tracing/value/chart_json_converter.html:54:37)\n    at Object.iterItems (/tracing/base/iteration_helpers.html:173:10)\n    at Object.tr.b.iterItems (/tracing/value/chart_json_converter.html:26:14)\n    at Object.iterItems (/tracing/base/iteration_helpers.html:173:10)\n    at Function.convertChartJson (/tracing/value/chart_json_converter.html:23:12)\n    at eval (D:\\src\\chrome\\src\\third_party\\catapult\\tracing\\tracing\\value\\convert_chart_json_cmdline.html:17:27)\n    at Object.loadHTMLFile (D:\\src\\chrome\\src\\third_party\\catapult\\third_party\\vinn\\vinn\\html_imports_loader.js:140:5)\n    at D:\\src\\chrome\\src\\third_party\\catapult\\third_party\\vinn\\vinn\\d8_bootstrap.js:150:19\n\n"
  returncode   : 1
  sp           : <subprocess.Popen object at 0x0495C0F0>
  stdin        : -1
  stdout       : -1
  v8_args      : []