NoSuchMethodError: The method '*' was called on null.

[old-traveler]

flutter 1.12.13
{StatckTrace=#0 _PagePosition.getPixelsFromPage (package:flutter/src/widgets/page_view.dart:366)
#1 PageController.animateToPage (package:flutter/src/widgets/page_view.dart:204)
#2 _TransformerPageViewState.onChangeNotifier (package:transformer_page_view/transformer_page_view.dart:606)
#3 ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:206)
#4 IndexController.next (package:transformer_page_view/index_controller.dart:30)
#5 _SwiperTimerMixin._onTimer (package:flutter_swiper/src/swiper.dart:370)
#6 _rootRunUnary (dart:async/zone.dart:1134)
#7 _CustomZone.runUnary (dart:async/zone.dart:1031)
#8 _CustomZone.runUnaryGuarded (dart:async/zone.dart:933)
#9 _CustomZone.bindUnaryCallbackGuarded. (dart:async/zone.dart:970)
#10 _rootRunUnary (dart:async/zone.dart:1138)
#11 _CustomZone.runUnary (dart:async/zone.dart:1031)
#12 _CustomZone.bindUnaryCallback. (dart:async/zone.dart:954)
#13 _Timer._runTimers (dart:isolate-patch/timer_impl.dart:384)
#14 _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:418)
#15 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:174)
, FlutterErrorDetail=}