src/Pure/Admin/build_release.scala

           {
             val getsettings = release.isabelle + Path.explode("lib/scripts/getsettings")
             execute_tar(tmp_dir, "-xzf " +
               File.bash_path(release.isabelle_archive) + " " + File.bash_path(getsettings))
             Isabelle_System.isabelle_id(root = tmp_dir + release.isabelle)
-              .getOrElse(error("Failed to determine ISABELLE_ID from " + release.isabelle_archive))
           })
 
       if (release.ident != archive_ident) {
         error("Mismatch of release identification " + release.ident +
           " vs. archive " + archive_ident)