Fix failing test (when run in isolation)

spec/muc.js

@@ -527,6 +527,7 @@
                     }).c('body').t(message).tree();
 
                 await view.model.onMessage(msg);
+                await u.waitUntil(()  => view.el.querySelector('.chat-msg__text a'));
                 view.el.querySelector('.chat-msg__text a').click();
                 await u.waitUntil(() => _converse.chatboxes.length === 3)
                 expect(_.includes(_converse.chatboxes.pluck('id'), 'coven@chat.shakespeare.lit')).toBe(true);