message: Prevent users from deleting their root ACLs
  This checks whether pathname indicates that the target is root, or whether the root ACL itself states that the target is root.
diff: @@ -612,14 +612,17 @@ UI.aclControl.ACLControlBox5 = function (subject, dom, noun, kb, callback) {
  var q = str.indexOf('//')
  var targetDocDir = ((q >= 0 && p < q + 2) || p < 0) ? null : str.slice(0, p + 1)
  - if (targetDocDir) {
  + // eslint-disable-next-line no-undef
  + const targetIsStorage = kb.holds(targetDoc, UI.ns.rdf('type'), UI.ns.space('Storage'), targetACLDoc) || (location && location.pathname === '/')
  +
  + if (!targetIsStorage && targetDocDir) {
  UI.acl.getACLorDefault($rdf.sym(targetDocDir), function (ok2, p22, targetDoc2, targetACLDoc2, defaultHolder2, defaultACLDoc2) {
  if (ok2) {
  prospectiveDefaultHolder = p22 ? targetDoc2 : defaultHolder2
  }
  addDefaultButton(prospectiveDefaultHolder)
  })
  - } else {
  + } else if (!targetIsStorage) {
  addDefaultButton()
  }
  