Enable Cmd key support in shortcuts

www/slide/inner.js

@@ -556,7 +556,6 @@ define([
     };
 
     var getThumbnailContainer = function () {
-        var $codeMirror = $('.CodeMirror');
         var $c = $('#cp-app-slide-editor');
         if ($c.hasClass('cp-app-slide-preview')) {
             return $('.cp-app-slide-frame').first()[0];