alpheus hash throws 'null reference' if the path being queried does not exist

[dgrechka]

(venv) dmitry[1869.train]@compute:/mnt/ssd/PetSimilarity-ML$ alpheus hash experiments/dgrechka/run3/
Actual disk version of the artefact experiments/dgrechka/run3/
System.NullReferenceException: Object reference not set to an instance of an object.
at ItisLab.Alpheus.CliRunner.run@129-36.Invoke(Tuple2 arg) in C:\repos\alpheus\Alpheus.CLI\Runner.fs:line 129 at Microsoft.FSharp.Primitives.Basics.List.iter[T](FSharpFunc2 f, FSharpList1 x) in E:\A\_work\130\s\src\fsharp\FSharp.Core\local.fs:line 91 at Microsoft.FSharp.Collections.ListModule.Iterate[T](FSharpFunc2 action, FSharpList1 list) in E:\A\_work\130\s\src\fsharp\FSharp.Core\list.fs:line 104 at ItisLab.Alpheus.CliRunner.run@127-35.Invoke(Tuple2 _arg13) in C:\repos\alpheus\Alpheus.CLI\Runner.fs:line 129
at ItisLab.Alpheus.Results.ResultBuilder.Bind[a2,a3,a4](FSharpResult2 m, FSharpFunc2 f) in C:\repos\alpheus\AlpheusCore\ResultBuilder.fs:line 16
at ItisLab.Alpheus.CliRunner.run@124-34.Invoke(Unit unitVar) in C:\repos\alpheus\Alpheus.CLI\Runner.fs:line 126
at ItisLab.Alpheus.Results.ResultBuilder.Run[m](FSharpFunc2 f) in C:\repos\alpheus\AlpheusCore\ResultBuilder.fs:line 31 at ItisLab.Alpheus.CliRunner.run(String programName, String workingDir, ParseResults1 parseResults) in C:\repos\alpheus\Alpheus.CLI\Runner.fs:line 123
at ItisLab.Alpheus.Program.main(String[] argv) in C:\repos\alpheus\Alpheus.CLI\Program.fs:line 42