Unhandled exception: NoSuchMethodError: The getter 'start' was called on null.

[SimonButtazzi]

Startet using docker run --rm tennox/linkcheck https://www.ion2s.com

got error:

Crawling...
Unhandled exception:
NoSuchMethodError: The getter 'start' was called on null.
Receiver: null
Tried calling: start
#0      _serializeSpan (package:linkcheck/src/origin.dart:37)
#1      Origin.toMap (package:linkcheck/src/origin.dart:29)
#2      Link.toMap (package:linkcheck/src/link.dart:60)
#3      FetchResults.toMap.<anonymous closure> (package:linkcheck/src/worker/fetch_results.dart:20)
#4      MappedListIterable.elementAt (dart:_internal/iterable.dart:415)
#5      ListIterator.moveNext (dart:_internal/iterable.dart:344)
#6      new _GrowableList._ofEfficientLengthIterable (dart:core-patch/growable_array.dart:189)
#7      new _GrowableList.of (dart:core-patch/growable_array.dart:150)
#8      new List.of (dart:core-patch/array_patch.dart:52)
#9      SetMixin.toList (dart:collection/set.dart:118)
#10     FetchResults.toMap (package:linkcheck/src/worker/fetch_results.dart:20)
#11     worker.<anonymous closure> (package:linkcheck/src/worker/worker.dart:193)
<asynchronous suspension>