modal widgets - how to close them

gistfile1.js

/*
This is a paraphrased version of some code I'm working on.

What I'm trying to achieve is:
- open a modal with a custom footer (see 'footer' property of the addTiddler call)
- the footer contains a $button widget with a custom message
- listen for the custom message on $tw.rootWidget and update localstorage to note the button has been clicked
- then close the modal and show another div

I've got as far as the last step. The event handler on $tw.rootWidget doesn't give me any
of the widgets that make up the modal, so I can't dispatch 'tw-close-tiddler' on them. Dispatch
'tw-close-tiddler' on $tw.rootWidget doesn't do anything (which I expect).

Is there a way grab a reference to the widgets in the modal so I can dispatch 'tw-close-tiddler' on them?
If not, is there another to close the modal I could use?

*/


var title = 'Terms & Conditions',
  message = $('.welcome-tool > div.card').html().replace('&','&');

$tw.wiki.addTiddler({
  title: title,
  text: message,
  footer: '<$button class="welcome-tool-submit btn btn-primary btn-lg btn-block disabled" message="welcome-tool-submit">Accept and Get Started</$button>'
});

$tw.rootWidget.addEventListener("welcome-tool-submit", function() {
  localStorage.setItem('ctrlio-terms-accepted', 'true');
  // TO-DO: close the widget and show the tools card
});

window.setTimeout(function() {
  if ($tw.modal.modalCount === 0) {
    $tw.modal.display(title);
  }
}, 10);