Fixed #531: a bug in the `DataSet` returning an empty object instead of `null` when no item was found when using both a filter and specifying fields.

HISTORY.md

@@ -9,11 +9,13 @@ http://visjs.org
 - Added option bindToWindow (default true) to choose whether the keyboard binds are global or to the network div.
 - Improved images handling so broken images are shown on all references of images that are broken.
 
-### DataSet
+### DataSet/DataView
 
 - Added property `length` holding the total number of items to the `DataSet`
   and `DataView`.
 - Added a method `refresh()` to the `DataView`, to update filter results.
+- Fixed a bug in the `DataSet` returning an empty object instead of `null` when
+  no item was found when using both a filter and specifying fields.
 
 ### Timeline
 

lib/DataSet.js

@@ -651,12 +651,16 @@ DataSet.prototype.map = function (callback, options) {
 
 /**
  * Filter the fields of an item
- * @param {Object} item
+ * @param {Object | null} item
  * @param {String[]} fields     Field names
- * @return {Object} filteredItem
+ * @return {Object | null} filteredItem or null if no item is provided
  * @private
  */
 DataSet.prototype._filterFields = function (item, fields) {
+  if (!item) { // item is null
+    return item;
+  }
+
   var filteredItem = {};
 
   for (var field in item) {