[FIX] website_mass_mailing: fixed the traceback on close modal dialog

The issue here is, the modal for the newsletter is part of the editable area,
and when we click on the 'close' button of that modal, it is destroyed but the
'summer note' tries to bind the events related to the button(because close is a button).

fixed the traceback, to disable invoking 'summer note' events on click of
the 'close' button on modal

task-2075232

X-original-commit: 110ea837903f3e6c67c1d0e0081073edea8852d1

addons/website_mass_mailing/static/src/js/website_mass_mailing.js

@@ -168,6 +168,9 @@ publicWidget.registry.newsletter_popup = publicWidget.Widget.extend({
         });
         this.massMailingPopup.opened().then(function () {
             var $modal = self.massMailingPopup.$modal;
+            $modal.find('header button.close').on('mouseup', function (ev) {
+                ev.stopPropagation();
+            });
             $modal.addClass('o_newsletter_modal');
             $modal.find('.oe_structure').attr('data-editor-message', _t('DRAG BUILDING BLOCKS HERE'));
             $modal.find('.modal-dialog').addClass('modal-dialog-centered');