set to unknown when there is no source

demo/elements/google-chart-elasticsearch/google-chart.html

@@ -542,7 +542,15 @@ Data can be provided in one of three ways:
       if (this.rows && this.rows.length > 0 && this.cols &&
         this.cols.length > 0) {
         // Create the data table from cols and rows.
-        // console.log(data)
+
+        //Check that there are not undefined elements
+        // If exists set it to unknown
+        for(var i = 0; i < this.rows.length ; i++){
+          if(this.rows[i][0] == undefined){
+            this.rows[i][0] = "Unknown";
+          }
+        }
+
         dataTable = new google.visualization.DataTable();
         dataTable.cols = this.cols;
         for (var i = 0; i < this.cols.length; i++) {
@@ -573,7 +581,6 @@ Data can be provided in one of three ways:
 
             // There is an error when rows have not the same length, we have to
             // delete unnecesary data from rows (undefined values)
-
             var numCols = 0;
             for(; this.rows[0][numCols] != undefined; numCols++);