AvoidUnusedPrivateFieldsAnalyzer NRE on dotnet/runtime CI

[kg]

  System.Runtime.Serialization.Schema -> /__w/1/s/artifacts/bin/System.Runtime.Serialization.Schema/Debug/net8.0/System.Runtime.Serialization.Schema.dll
CSC : error AD0001: Analyzer 'Microsoft.CodeQuality.Analyzers.Maintainability.AvoidUnusedPrivateFieldsAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'. [/__w/1/s/src/libraries/System.Linq/src/System.Linq.csproj::TargetFramework=net9.0-android]
##[error]CSC(0,0): error AD0001: (NETCORE_ENGINEERING_TELEMETRY=Build) Analyzer 'Microsoft.CodeQuality.Analyzers.Maintainability.AvoidUnusedPrivateFieldsAnalyzer' threw an exception of type 'System.NullReferenceException' with message 'Object reference not set to an instance of an object.'.
  System.Resources.Extensions -> /__w/1/s/artifacts/bin/System.Resources.Extensions/Debug/net462/System.Resources.Extensions.dll

https://github.com/dotnet/runtime/pull/106099/checks?check_run_id=28679396406

https://dev.azure.com/dnceng-public/public/_build/results?buildId=773446&view=logs&jobId=e80acbf0-bc87-577c-4c46-0016b0794913&j=e80acbf0-bc87-577c-4c46-0016b0794913&t=f0fa9d72-e49a-5249-4d28-1199014b9857

[kg]

Looks like this is tracked by dotnet/dnceng#3305