Supervised user import dialog: disable "ok" button when no user is selected

chrome/browser/resources/options/supervised_user_import.js

Index: chrome/browser/resources/options/supervised_user_import.js
diff --git a/chrome/browser/resources/options/supervised_user_import.js b/chrome/browser/resources/options/supervised_user_import.js
index e6b436aaccdcc2f079374e26d4aaa9965c5723dc..2eb2156b73589df836843ccc73b8fbe446a937d9 100644
--- a/chrome/browser/resources/options/supervised_user_import.js
+++ b/chrome/browser/resources/options/supervised_user_import.js
@@ -45,11 +45,8 @@ cr.define('options', function() {
 
       supervisedUserList.addEventListener('change', function(event) {
         var supervisedUser = supervisedUserList.selectedItem;
-        if (!supervisedUser)
-          return;
-
         $('supervised-user-import-ok').disabled =
-          supervisedUserList.selectedItem.onCurrentDevice;
+            !supervisedUser || supervisedUser.onCurrentDevice;
       });
 
       var self = this;