Crash when compiling null, at character offset null: Null check operator used on a null value IN FLUTTER DEMO

I am learning flutter. today after finishing the installations and running the default flutter application i got this error, i did not touch any of the default code. please help me i have been applying the possible solutions for hours but nothing works, i even reinstalled everything.

I have everything installed in the latest version and 0 issues in flutter doctor.

  Crash when compiling null,
at character offset null:
Null check operator used on a null value
#0      InferableTypeBuilderMixin.type (package:front_end/src/fasta/builder/type_builder.dart:392:29)
#1      InferableTypeBuilder.inferType (package:front_end/src/fasta/builder/omitted_type_builder.dart:155:12)
#2      SourceLoader.performTopLevelInference (package:front_end/src/fasta/source/source_loader.dart:2358:19)
#3      KernelTarget.buildOutlines.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:532:14)
<asynchronous suspension>
#4      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#5      _buildInternal (package:front_end/src/kernel_generator_impl.dart:139:7)
<asynchronous suspension>
#6      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#7      generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#8      generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#9      kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#10     SingleShotCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:412:11)
<asynchronous suspension>
#11     Compiler.compile.<anonymous closure> (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:221:45)
<asynchronous suspension>
#12     _processLoadRequest (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:914:37)
<asynchronous suspension>


#0      InferableTypeBuilderMixin.type (package:front_end/src/fasta/builder/type_builder.dart:392:29)
#1      InferableTypeBuilder.inferType (package:front_end/src/fasta/builder/omitted_type_builder.dart:155:12)
#2      SourceLoader.performTopLevelInference (package:front_end/src/fasta/source/source_loader.dart:2358:19)
#3      KernelTarget.buildOutlines.<anonymous closure> (package:front_end/src/fasta/kernel/kernel_target.dart:532:14)
<asynchronous suspension>
#4      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#5      _buildInternal (package:front_end/src/kernel_generator_impl.dart:139:7)
<asynchronous suspension>
#6      withCrashReporting (package:front_end/src/fasta/crash.dart:122:12)
<asynchronous suspension>
#7      generateKernel.<anonymous closure> (package:front_end/src/kernel_generator_impl.dart:47:12)
<asynchronous suspension>
#8      generateKernel (package:front_end/src/kernel_generator_impl.dart:46:10)
<asynchronous suspension>
#9      kernelForModule (package:front_end/src/api_prototype/kernel_generator.dart:100:11)
<asynchronous suspension>
#10     SingleShotCompilerWrapper.compileInternal (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:412:11)
<asynchronous suspension>
#11     Compiler.compile.<anonymous closure> (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:221:45)
<asynchronous suspension>
#12     _processLoadRequest (file:///C:/b/s/w/ir/cache/builder/sdk/pkg/vm/bin/kernel_service.dart:914:37)
<asynchronous suspension>