Null data crash fix

Author: nikitaeverywhere

package.json

@@ -1,7 +1,7 @@
 {
   "name": "LightPivotTable",
   "author": "ZitRo",
-  "version": "1.6.11",
+  "version": "1.6.12",
   "description": "A lightweight pivot table for MDX2JSON source for InterSystems Cache",
   "main": "test/testServer.js",
   "repository": {

source/js/DataController.js

@@ -82,7 +82,7 @@ DataController.prototype.popData = function () {
 
 DataController.prototype.getData = function () {
 
-    return this._dataStack[this._dataStack.length - 1].data;
+    return this._dataStack[this._dataStack.length - 1].data || {};
 
 };