Added notification service redirect on add button

If no notification services are setup, clicking the add button on the home page will now redirect you to the notification services page instead of doing nothing.

frontend/static/js/add.js

@@ -39,6 +39,8 @@ function addReminder() {
 function showAdd() {
 	if (!document.getElementById('add-entry').classList.contains('error')) {
 		showWindow('add');
+	} else {
+		showWindow('notification');
 	};
 };