[BUG] NullReferenceException thrown from Azure.Storage.Files.DataLake.DataLakeFileClient.UploadAsync when specifying high StorageTransferOptions.MaximumConcurrency

Describe the bug This appears like a regression in the latest version (does not reproduce in 12.2.2):

System.NullReferenceException: Object reference not set to an instance of an object.
   at Azure.Storage.Files.DataLake.DataLakeFileClient.<>c__DisplayClass83_0.<<GetPartitionedUploaderBehaviors>b__2>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at Azure.Storage.PartitionedUploader`2.StagePartitionAndDisposeInternal(SlicedStream partition, Int64 offset, TServiceSpecificArgs args, IProgress`1 progressHandler, Boolean async, CancellationToken cancellationToken)
   at Azure.Storage.PartitionedUploader`2.UploadInParallelAsync(Stream content, Nullable`1 contentLength, Int64 blockSize, TServiceSpecificArgs args, IProgress`1 progressHandler, CancellationToken cancellationToken)
   at Azure.Storage.PartitionedUploader`2.UploadInParallelAsync(Stream content, Nullable`1 contentLength, Int64 blockSize, TServiceSpecificArgs args, IProgress`1 progressHandler, CancellationToken cancellationToken)
   at Azure.Storage.PartitionedUploader`2.UploadInternal(Stream content, TServiceSpecificArgs args, IProgress`1 progressHandler, Boolean async, CancellationToken cancellationToken)
   at Azure.Storage.Files.DataLake.DataLakeFileClient.StagedUploadInternal(Stream content, DataLakeFileUploadOptions options, Boolean async, CancellationToken cancellationToken)
   at Azure.Storage.Files.DataLake.DataLakeFileClient.UploadAsync(String path, DataLakeFileUploadOptions options, CancellationToken cancellationToken)
   at Azure.Storage.Files.DataLake.DataLakeFileClient.UploadAsync(String path, PathHttpHeaders httpHeaders, DataLakeRequestConditions conditions, IProgress`1 progressHandler, StorageTransferOptions transferOptions, CancellationToken cancellationToken)

To Reproduce Steps to reproduce the behavior (include a code snippet, screenshot, or any additional information that might help us reproduce the issue)

await fileClient.UploadAsync(someLargeFileLike2GB, transferOptions: new StorageTransferOptions
            { 
                MaximumConcurrency = 500,
                InitialTransferLength = 1024 * 1024 * 4,
                MaximumTransferLength = 1024 * 1024 * 4
            })

Environment:

• Name and version of the Library package used: Azure.Storage.Files.DataLake 12.3.1
• Hosting platform or OS and .NET runtime version:

.NET Core SDK (reflecting any global.json):
 Version:   3.1.401
 Commit:    5b6f5e5005

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18363
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\3.1.401\

Host (useful for support):
  Version: 3.1.7
  Commit:  fcfdef8d6b

.NET Core SDKs installed:
  1.1.11 [C:\Program Files\dotnet\sdk]
  1.1.14 [C:\Program Files\dotnet\sdk]
  2.1.202 [C:\Program Files\dotnet\sdk]
  2.1.503 [C:\Program Files\dotnet\sdk]
  2.1.514 [C:\Program Files\dotnet\sdk]
  2.1.515 [C:\Program Files\dotnet\sdk]
  3.1.302 [C:\Program Files\dotnet\sdk]
  3.1.401 [C:\Program Files\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.All 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.18 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.All 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.All]
  Microsoft.AspNetCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.18 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 1.0.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.0.16 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.1.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 1.1.13 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.0.9 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.18 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.19 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 2.1.21 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 3.1.7 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

• IDE and version : Visual Studio 16.7.2

[sumantmehtams]

Adding @seanmcc-msft to take a look.

[jsquire]

Thank you for your feedback. Tagging and routing to the team best able to assist.