(js) Prohibit subscribing a user with no rights

UI/WebServerResources/js/Common/AclController.js

@@ -26,6 +26,7 @@
     vm.addUser = addUser;
     vm.selectAllRights = selectAllRights;
     vm.selectUser = selectUser;
+    vm.hasNoRight = hasNoRight;
     vm.showRights = showRights;
     vm.confirmation = { showing: false,
                         message: ''};
@@ -104,6 +105,10 @@
       }
     }
 
+    function hasNoRight(user) {
+      return folder.$acl.$hasNoRight(user);
+    }
+
     function showRights(user) {
       return vm.selectedUid == user.uid && !user.inactive;
     }