Bug 422590: menu bar disabled when customizing toolbar in popup window, r=mano, a=beltzner

browser/base/content/browser.js

@@ -2955,8 +2955,13 @@ const BrowserSearch = {
    */
   updateSearchButton: function() {
     var searchBar = this.searchBar;
-    if (!searchBar)
+    
+    // The search bar binding might not be applied even though the element is
+    // in the document (e.g. when the navigation toolbar is hidden), so check
+    // for .searchButton specifically.
+    if (!searchBar || !searchBar.searchButton)
       return;
+
     var engines = gBrowser.mCurrentBrowser.engines;
     if (engines && engines.length > 0)
       searchBar.searchButton.setAttribute("addengines", "true");