fixed error

src/app/ui/card.js

@@ -34,10 +34,12 @@ module.exports = class Card {
     function trigger (el) {
       var body = self._view.cardBody
       var status = self._view.statusBar
+      if (el.classList) {
         el.classList.toggle('fa-angle-up')
         var arrow = el.classList.toggle('fa-angle-down') ? 'up' : 'down'
         self.event.trigger('expandCollapseCard', [arrow, body, status])
       }
+    }
 
     // HTML
     self._view.el = yo`