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/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
+};