fixed creation and deletion of empty groups when there are not yet items

examples/graph2d/15_streaming_data.html

@@ -40,7 +40,6 @@
   // create a graph2d with an (currently empty) dataset
   var container = document.getElementById('visualization');
   var dataset = new vis.DataSet();
-  var now = vis.moment();
 
   var options = {
     start: vis.moment().add(-30, 'seconds'), // changed so its faster

lib/timeline/component/LineGraph.js

@@ -441,26 +441,21 @@ LineGraph.prototype._updateAllGroupData = function () {
  * @protected
  */
 LineGraph.prototype._updateUngrouped = function() {
-  if (this.itemsData != null) {
-//    var t0 = new Date();
-    var group = {id: UNGROUPED, content: this.options.defaultGroup};
-    this._updateGroup(group, UNGROUPED);
+  if (this.itemsData && this.itemsData != null) {
     var ungroupedCounter = 0;
-    if (this.itemsData) {
-      for (var itemId in this.itemsData._data) {
-        if (this.itemsData._data.hasOwnProperty(itemId)) {
-          var item = this.itemsData._data[itemId];
-          if (item != undefined) {
-            if (item.hasOwnProperty('group')) {
-              if (item.group === undefined) {
-                item.group = UNGROUPED;
-              }
-            }
-            else {
+    for (var itemId in this.itemsData._data) {
+      if (this.itemsData._data.hasOwnProperty(itemId)) {
+        var item = this.itemsData._data[itemId];
+        if (item != undefined) {
+          if (item.hasOwnProperty('group')) {
+            if (item.group === undefined) {
               item.group = UNGROUPED;
             }
-            ungroupedCounter = item.group == UNGROUPED ? ungroupedCounter + 1 : ungroupedCounter;
           }
+          else {
+            item.group = UNGROUPED;
+          }
+          ungroupedCounter = item.group == UNGROUPED ? ungroupedCounter + 1 : ungroupedCounter;
         }
       }
     }
@@ -472,6 +467,10 @@ LineGraph.prototype._updateUngrouped = function() {
       this.yAxisLeft.removeGroup(UNGROUPED);
       this.yAxisRight.removeGroup(UNGROUPED);
     }
+    else {
+      var group = {id: UNGROUPED, content: this.options.defaultGroup};
+      this._updateGroup(group, UNGROUPED);
+    }
   }
   else {
     delete this.groups[UNGROUPED];