Changes to default apps promo per ui leads:

chrome/browser/resources/ntp/apps.js

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 var MAX_APPS_PER_ROW = [];
 MAX_APPS_PER_ROW[LayoutMode.SMALL] = 4;
 MAX_APPS_PER_ROW[LayoutMode.NORMAL] = 6;
 
 // The URL prefix used in the app link 'ping' attributes.
 var PING_APP_LAUNCH_PREFIX = 'record-app-launch';
@@ skipping 60 matching lines @@
   } else {
     appsSection.classList.remove('disabled');
   }
   addClosedMenuFooter(apps.menu, 'apps', MINIMIZED_APPS, Section.APPS);
 
   apps.loaded = true;
   if (apps.showPromo)
     document.documentElement.classList.add('apps-promo-visible');
   else
     document.documentElement.classList.remove('apps-promo-visible');
-  $('apps-promo-link').setAttribute('ping', appsPromoPing);
+
+  var appsPromoLink = $('apps-promo-link');
+  if (appsPromoLink)
+    appsPromoLink.setAttribute('ping', appsPromoPing);
   maybeDoneLoading();
 
   if (isDoneLoading()) {
     if (!apps.showPromo && data.apps.length >= MAX_APPS_PER_ROW[layoutMode])
       webStoreEntry.classList.add('loner');
     else
       webStoreEntry.classList.remove('loner');
 
     updateMiniviewClipping(appsMiniview);
     layoutSections();
@@ skipping 262 matching lines @@
     createWebStoreClosedMenuElement: function() {
       var a = document.createElement('a');
       a.textContent = localStrings.getString('web_store_title');
       a.href = localStrings.getString('web_store_url');
       a.style.backgroundImage = url('chrome://theme/IDR_PRODUCT_LOGO_16');
       a.className = 'item';
       return a;
     }
   };
 })();