System.ArgumentNullException: Value cannot be null.
Parameter name: path
   at Dropbox.Api.Files.ListFolderArg..ctor(String path, Boolean recursive, Boolean includeMediaInfo, Boolean includeDeleted, Boolean includeHasExplicitSharedMembers, Boolean includeMountedFolders, Nullable`1 limit, SharedLink sharedLink, TemplateFilterBase includePropertyGroups, Boolean includeNonDownloadableFiles)
   at Dropbox.Api.Files.Routes.FilesUserRoutes.ListFolderAsync(String path, Boolean recursive, Boolean includeMediaInfo, Boolean includeDeleted, Boolean includeHasExplicitSharedMembers, Boolean includeMountedFolders, Nullable`1 limit, SharedLink sharedLink, TemplateFilterBase includePropertyGroups, Boolean includeNonDownloadableFiles)
   at ReadingEmails.Readmail.<ListFilesAndDirectoriesAsync>d__45.MoveNext() in C:\CODES\MailProject\ReadingEmails\Readmail.cs:line 3072