I might be missing something but the reason you don't have an ID in javascript code is because you don't have any data attributes defined on your button.
So say you are using your edit button (I added Edit as your link should even appear as its an empty anchor tag):
<a href="#edit-event-modal">Edit</a>
In your javascript you access the calling button and Id as such
var button = $(event.relatedTarget);
var recipient = button.data('id');
This is not how i do this functionality so I'm not sure if relatedTarget works. However, your recipient should always be null because there is no data-id attribute on your edit button link. You need to do the following to get some value in your recipient
<a href="#edit-event-modal">Edit</a>
<!--