java.lang.Exception: NoSuchMethodError: The getter 'millisecondsSinceEpoch' was called on null.

[kw2019ltd]

Non-fatal Exception: java.lang.Exception: NoSuchMethodError: The getter 'millisecondsSinceEpoch' was called on null.
Receiver: null
Tried calling: millisecondsSinceEpoch
at sortBy.(utils.dart:31)
at .sortBy(utils.dart:26)
at FileManager.recentFilesAndDirs(file_manager.dart:52)
at _DownloadPageState._initFiles(download_page.dart:68)
at _DownloadPageState.initDownloadsDirectoryState(download_page.dart:60)
at _DownloadPageState.initState(download_page.dart:36)
at StatefulElement._firstBuild(framework.dart:4355)
at ComponentElement.mount(framework.dart:4201)
at Element.inflateWidget(framework.dart:3194)
at Element.updateChild(framework.dart:2988)
at SingleChildRenderObjectElement.mount(framework.dart:5445)
at Element.inflateWidget(framework.dart:3194)
at Element.updateChild(framework.dart:2988)
at SingleChildRenderObjectElement.mount(framework.dart:5445)
at Element.inflateWidget(framework.dart:3194)
at Element.updateChild(framework.dart:2988)
at ComponentElement.performRebuild(framework.dart:4243)
at Element.rebuild(framework.dart:3947)
at ComponentElement._firstBuild(framework.dart:4206)
at ComponentElement.mount(framework.dart:4201)
at Element.inflateWidget(framework.dart:3194)
at Element.updateChild(framework.dart:2988)
at ComponentElement.performRebuild(framework.dart:4243)
at Element.rebuild(framework.dart:3947)
at ComponentElement._firstBuild(framework.dart:4206)
at ComponentElement.mount(framework.dart:4201)
at ParentDataElement.mount(framework.dart:4617)
at Element.inflateWidget(framework.dart:3194)
at Element.updateChild(framework.dart:2988)
at ComponentElement.performRebuild(framework.dart:4243)
at Element.rebuild(framework.dart:3947)
at ComponentElement._firstBuild(framework.dart:4206)
at StatefulElement._firstBuild(framework.dart:4381)
at ComponentElement.mount(framework.dart:4201)
at Element.inflateWidget(framework.dart:3194)
at Element.updateChild(framework.dart:2988)
at ComponentElement.performRebuild(framework.dart:4243)
at Element.rebuild(framework.dart:3947)
at ComponentElement._firstBuild(framework.dart:4206)
at ComponentElement.mount(framework.dart:4201)
at Element.inflateWidget(framework.dart:3194)
at Element.updateChild(framework.dart:2988)
at SliverMultiBoxAdaptorElement.updateChild(sliver.dart:1288)
at SliverMultiBoxAdaptorElement.createChild.(sliver.dart:1273)
at BuildOwner.buildScope(framework.dart:2412)
at SliverMultiBoxAdaptorElement.createChild(sliver.dart:1266)
at RenderSliverMultiBoxAdaptor._createOrObtainChild.(sliver_multi_box_adaptor.dart:354)
at RenderObject.invokeLayoutCallback.(object.dart:1823)
at PipelineOwner._enableMutationsToDirtySubtrees(object.dart:875)
at RenderObject.invokeLayoutCallback(object.dart:1823)
at RenderSliverMultiBoxAdaptor._createOrObtainChild(sliver_multi_box_adaptor.dart:343)
at RenderSliverMultiBoxAdaptor.insertAndLayoutChild(sliver_multi_box_adaptor.dart:489)
at RenderSliverFixedExtentBoxAdaptor.performLayout(sliver_fixed_extent_list.dart:255)
at RenderObject.layout(object.dart:1724)
at RenderSliverEdgeInsetsPadding.performLayout(sliver_padding.dart:134)
at _RenderSliverFractionalPadding.performLayout(sliver.dart:1165)
at RenderObject.layout(object.dart:1724)
at RenderViewportBase.layoutChildSequence(viewport.dart:410)
at RenderViewport._attemptLayout(viewport.dart:1367)
at RenderViewport.performLayout(viewport.dart:1285)
at RenderObject._layoutWithoutResize(object.dart:1584)
at PipelineOwner.flushLayout(object.dart:844)
at RendererBinding.drawFrame(binding.dart:344)
at WidgetsBinding.drawFrame(binding.dart:774)
at RendererBinding._handlePersistentFrameCallback(binding.dart:283)
at SchedulerBinding._invokeFrameCallback(binding.dart:1102)
at SchedulerBinding.handleDrawFrame(binding.dart:1041)
at SchedulerBinding._handleDrawFrame(binding.dart:957)