GetBuildVersion task fails with ArgumentNullException

[dfederm]

The "Nerdbank.GitVersioning.Tasks.GetBuildVersion" task failed unexpectedly.
System.ArgumentNullException: Array cannot be null.
Parameter name: bytes
   at System.Text.Encoding.GetString(Byte* bytes, Int32 byteCount)
   at Nerdbank.GitVersioning.ManagedGit.GitRepository.GetString(ReadOnlySpan`1 bytes)
   at Nerdbank.GitVersioning.ManagedGit.GitCommitReader.TryReadAuthor(ReadOnlySpan`1 line, GitSignature& signature)
   at Nerdbank.GitVersioning.ManagedGit.GitCommitReader.Read(ReadOnlySpan`1 commit, GitObjectId sha, Boolean readAuthor)
   at Nerdbank.GitVersioning.ManagedGit.GitCommitReader.Read(Stream stream, GitObjectId sha, Boolean readAuthor)
   at Nerdbank.GitVersioning.ManagedGit.GitRepository.GetCommit(GitObjectId sha, Boolean readAuthor)
   at Nerdbank.GitVersioning.Managed.ManagedGitContext.get_GitCommitDate()
   at Nerdbank.GitVersioning.Tasks.GetBuildVersion.ExecuteInner()
   at MSBuildExtensionTask.ContextAwareTask.Execute()
   at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
   at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext()

I can share the specific commit offline, but the issue seems to be due to the author not having a proper email address (it's a service principal in Azure DevOps). ie the "git log" shows: Author: Something <> (where "Something" is some other redacted string).