src/Pure/Tools/dotnet_setup.scala

           progress.echo("Platform " + platform.name + " ...")
           platform.check()
           if (platform_dir.is_dir && force) Isabelle_System.rm_tree(platform_dir)
           val script =
             platform.exec + " " + File.bash_platform_path(install) +
-              (if (version.nonEmpty) " -Version " + Bash.string(version) else "") +
+              if_proper(version, " -Version " + Bash.string(version)) +
               " -Architecture " + Bash.string(platform.arch) +
-              (if (platform.os.nonEmpty) " -OS " + Bash.string(platform.os) else "") +
+              if_proper(platform.os, " -OS " + Bash.string(platform.os)) +
               " -InstallDir " + Bash.string(platform.name) +
               (if (dry_run) " -DryRun" else "") +
               " -NoPath"
           progress.bash(script, echo = verbose,
             cwd = if (dry_run) null else component_dir.path.file).check