preload: use page_params only when it exists.

This PR adds a params-util.js file which checks wheather the
page_params exists or not.

Fixes: #517.

app/renderer/js/notification/index.js

@@ -4,6 +4,7 @@ const {
   remote: { app }
 } = require('electron');
 
+const params = require('../utils/params-util.js');
 const DefaultNotification = require('./default-notification');
 const { appId, loadBots } = require('./helpers');
 
@@ -19,9 +20,8 @@ if (process.platform === 'darwin') {
 }
 
 window.addEventListener('load', () => {
-	// Call this function only when user is logged in
 	// eslint-disable-next-line no-undef, camelcase
-	if (page_params.realm_uri) {
+	if (params.isPageParams() && page_params.realm_uri) {
 		loadBots();
 	}
 });

app/renderer/js/preload.js

@@ -5,6 +5,7 @@ const SetupSpellChecker = require('./spellchecker');
 
 const ConfigUtil = require(__dirname + '/utils/config-util.js');
 const LinkUtil = require(__dirname + '/utils/link-util.js');
+const params = require(__dirname + '/utils/params-util.js');
 
 // eslint-disable-next-line import/no-unassigned-import
 require('./notification');
@@ -42,16 +43,15 @@ process.once('loaded', () => {
 
 // To prevent failing this script on linux we need to load it after the document loaded
 document.addEventListener('DOMContentLoaded', () => {
+	if (params.isPageParams()) {
 	// Get the default language of the server
 		const serverLanguage = page_params.default_language; // eslint-disable-line no-undef, camelcase
-
 		if (serverLanguage) {
 			// Set spellcheker language
 			ConfigUtil.setConfigItem('spellcheckerLanguage', serverLanguage);
 			// Init spellchecker
 			SetupSpellChecker.init();
 		}
-
 		// redirect users to network troubleshooting page
 		const getRestartButton = document.querySelector('.restart_get_events_button');
 		if (getRestartButton) {
@@ -59,10 +59,8 @@ document.addEventListener('DOMContentLoaded', () => {
 				ipcRenderer.send('forward-message', 'reload-viewer');
 			});
 		}
-
 		// Open image attachment link in the lightbox instead of opening in the default browser
 		const { $, lightbox } = window;
-
 		$('#main_div').on('click', '.message_content p a', function (e) {
 			const url = $(this).attr('href');
 
@@ -82,6 +80,7 @@ document.addEventListener('DOMContentLoaded', () => {
 				lightbox.open($img);
 			}
 		});
+	}
 });
 
 // Clean up spellchecker events after you navigate away from this page;

app/renderer/js/utils/params-util.js

@@ -0,0 +1,15 @@
+// This util function returns the page params if they're present else returns null
+function isPageParams() {
+	let webpageParams = null;
+	try {
+		// eslint-disable-next-line no-undef, camelcase
+		webpageParams = page_params;
+	} catch (err) {
+		webpageParams = null;
+	}
+	return webpageParams;
+}
+
+module.exports = {
+	isPageParams
+};