Backport PR #8164: replace undefined by empty string to get aroung bug in ie

Could close  #8161 ...need to test.

IPython/html/static/notebook/js/kernelselector.js

@@ -273,7 +273,7 b' define(['
 
     KernelSelector.prototype.new_notebook = function (kernel_name) {
         
-        var w = window.open(undefined, IPython._target);
+        var w = window.open('', IPython._target);
         // Create a new notebook in the same path as the current
         // notebook's path.
         var that = this;

IPython/html/static/notebook/js/menubar.js

@@ -76,7 +76,7 b' define(['
             notebook_path
         ) + "?download=" + download.toString();
         
-        var w = window.open(undefined, IPython._target);
+        var w = window.open('', IPython._target);
         if (this.notebook.dirty) {
             this.notebook.save_notebook().then(function() {
                 w.location = url;

IPython/html/static/notebook/js/notebook.js

@@ -2043,7 +2043,7 b' define(function (require) {'
     Notebook.prototype.copy_notebook = function () {
         var that = this;
         var base_url = this.base_url;
-        var w = window.open(undefined, IPython._target);
+        var w = window.open('', IPython._target);
         var parent = utils.url_path_split(this.notebook_path)[0];
         this.contents.copy(this.notebook_path, parent).then(
             function (data) {

IPython/html/static/tree/js/notebooklist.js

@@ -73,7 +73,7 b' define(['
         if (!NotebookList._bound_singletons) {
             NotebookList._bound_singletons = true;
             $('#new-file').click(function(e) {
-                var w = window.open(undefined, IPython._target);
+                var w = window.open('', IPython._target);
                 that.contents.new_untitled(that.notebook_path || '', {type: 'file', ext: '.txt'}).then(function(data) {
                     var url = utils.url_join_encode(
                         that.base_url, 'edit', data.path