Toggling spy panel no longer throws an error (#8906)

Backports PR #8877

**Commit 1:**
Toggling spy panel no longer throws an error

* Original sha: 0de553d
* Authored by Thomas Neirynck <thomas@elastic.co> on 2016-10-28T18:06:05Z

**Commit 2:**
Complete existence check before using handler

* Original sha: 6fad2be
* Authored by Thomas Neirynck <thomas@elastic.co> on 2016-10-31T14:11:40Z

src/ui/public/filter_bar/filter_bar.js

@@ -1,7 +1,5 @@
 import _ from 'lodash';
 import template from 'ui/filter_bar/filter_bar.html';
-import moment from 'moment';
-import angular from 'angular';
 import 'ui/directives/json_input';
 import filterAppliedAndUnwrap from 'ui/filter_bar/lib/filter_applied_and_unwrap';
 import FilterBarLibMapAndFlattenFiltersProvider from 'ui/filter_bar/lib/map_and_flatten_filters';

src/ui/public/vislib/lib/handler/handler.js

@@ -20,7 +20,6 @@ export default function HandlerBaseClass(Private) {
    */
   class Handler {
     constructor(vis, opts) {
-
       this.data = opts.data || new Data(vis.data, vis._attr, vis.uiState);
       this.vis = vis;
       this.el = vis.el;
@@ -78,7 +77,6 @@ export default function HandlerBaseClass(Private) {
        */
       this.disable = this.chartEventProxyToggle('off');
     }
-
     /**
      * Validates whether data is actually present in the data object
      * used to render the Vis. Throws a no results error if data is not

src/ui/public/visualize/visualize_legend.js

@@ -1,8 +1,5 @@
 import _ from 'lodash';
 import html from 'ui/visualize/visualize_legend.html';
-import $ from 'jquery';
-import d3 from 'd3';
-import findByParam from 'ui/utils/find_by_param';
 import VislibLibDataProvider from 'ui/vislib/lib/data';
 import VislibComponentsColorColorProvider from 'ui/vislib/components/color/color';
 import FilterBarFilterBarClickHandlerProvider from 'ui/filter_bar/filter_bar_click_handler';
@@ -18,7 +15,7 @@ uiModules.get('kibana')
   return {
     restrict: 'E',
     template: html,
-    link: function ($scope, $elem) {
+    link: function ($scope) {
       let $state = getAppState();
       let clickHandler = filterBarClickHandler($state);
       $scope.open = $scope.uiState.get('vis.legendOpen', true);
@@ -32,7 +29,11 @@ uiModules.get('kibana')
       $scope.highlight = function (event) {
         let el = event.currentTarget;
         let handler = $scope.renderbot.vislibVis.handler;
-        if (!handler) return;
+
+        //there is no guarantee that a Chart will set the highlight-function on its handler
+        if (!handler || typeof handler.highlight !== 'function') {
+          return;
+        }
         handler.highlight.call(el, handler.el);
       };
 
@@ -110,7 +111,7 @@ uiModules.get('kibana')
         data = data.columns || data.rows || [data];
         if (type === 'pie') return Data.prototype.pieNames(data);
         return getSeriesLabels(data);
-      };
+      }
 
       function getSeriesLabels(data) {
         let values = data.map(function (chart) {