The `initOnEvents` was used to get the notification sound file and
trigger the 30 second loop, but since the function was replaced to using
class syntax, the removeEvent listener was not working. This PR fixes it
by reverting to the old syntax but moving it inside the constructor
instead and also adding a `once: true` to ensure it is always removed
automatically
This issue is an extremely narrow edge case that does not affect the app functionality. It occurs here
1. `executeRecurringNotification` is the method that sets a timeout of 30 seconds and pings as required
2. This method is triggered when one of the following events happen `click`, `touchstart`, `keypress`, `keydown`
3. The class in question is initalized before the Vue app is mounted in `application.js`, the vue app is mounted on `window.onload` event
4. In a case where the Vue app is not created (i.e. `window.onload` event is not fired) within 30 seconds of a user input, this error occurs.
