Fix memory leak in leafletControlHelpers

Fixes issue #279.

Author: aripekkako

src/directives/controls.js

@@ -19,6 +19,10 @@ angular.module('ui-leaflet').directive('controls', function (leafletLogger, leaf
             var leafletControls = {};
             var errorHeader = leafletHelpers.errorHeader + ' [Controls] ';
 
+            scope.$on('$destroy', function () {
+                leafletControlHelpers.destroyMapLayersControl(scope.mapId);
+            });
+
             controller.getMap().then(function(map) {
 
                 leafletScope.$watchCollection('controls', function(newControls) {

src/directives/layers.js

@@ -23,6 +23,10 @@ angular.module('ui-leaflet').directive('layers', function (leafletLogger, $q, le
                 updateLayersControl = leafletControlHelpers.updateLayersControl,
                 isLayersControlVisible = false;
 
+            scope.$on('$destroy', function () {
+                leafletControlHelpers.destroyMapLayersControl(scope.mapId);
+            });
+
             controller.getMap().then(function(map) {
 
                 // We have baselayers to add to the map

src/services/leafletControlHelpers.js

@@ -194,6 +194,10 @@ angular.module('ui-leaflet').factory('leafletControlHelpers', function ($rootSco
                 map.addControl(_layersControl);
             }
             return mustBeLoaded;
+        },
+
+        destroyMapLayersControl: function(mapId) {
+            delete _controls[mapId];
         }
     };
 });