RED-7973: add null checks

Author: aritra_chakraborty

package.json

@@ -58,8 +58,7 @@
     "babel-plugin-add-module-exports": "^0.2.1",
     "babel-preset-es2015": "^6.24.1",
     "chai": "^3.5.0",
-    "eslint": "^3.19.0",
-    "eslint-loader": "^1.7.1",
+    "eslint-loader": "^2.0.0",
     "mocha": "^3.4.1",
     "rollup-plugin-commonjs": "^8.0.2",
     "rollup-plugin-node-resolve": "^3.0.0",
@@ -68,6 +67,7 @@
     "yards": "^0.1.4"
   },
   "dependencies": {
+    "eslint": "^3.19.0",
     "fusioncharts": "^3.13.0",
     "vue": "^2.3.3"
   }

src/vue-fusioncharts.js

@@ -121,11 +121,13 @@ export default (FC) => {
         },
         methods: {
             attachListeners: function (){
-                Object.keys(this.$listeners).forEach((event)=>{
-                    this.chartObj.addEventListener(event, (e)=>{
-                        this.$emit(event, e);
+                if(this.$listeners && typeof this.$listeners === 'object'){
+                    Object.keys(this.$listeners).forEach((event)=>{
+                        this.chartObj.addEventListener(event, (e)=>{
+                            this.$emit(event, e);
+                        });
                     });
-                });
+                }
             },
             setLastOptions: function (config) {
                 this._oldOptions = Object.assign({}, config);