Fixes a DCHECK failure while invoking permission link

chrome/browser/ui/gtk/extensions/extension_install_dialog_gtk.cc

 // Copyright (c) 2012 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.
 
 #include <gtk/gtk.h>
 
 #include "base/i18n/rtl.h"
 #include "base/string_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/extensions/bundle_installer.h"
@@ skipping 117 matching lines @@
   dialog_ = gtk_dialog_new_with_buttons(
       UTF16ToUTF8(prompt.GetDialogTitle()).c_str(),
       parent,
       GTK_DIALOG_MODAL,
       NULL);
   GtkWidget* close_button = gtk_dialog_add_button(
       GTK_DIALOG(dialog_),
       prompt.HasAbortButtonLabel() ?
           UTF16ToUTF8(prompt.GetAbortButtonLabel()).c_str() : GTK_STOCK_CANCEL,
       GTK_RESPONSE_CLOSE);
-  gtk_dialog_add_button(
-      GTK_DIALOG(dialog_),
-      UTF16ToUTF8(prompt.GetAcceptButtonLabel()).c_str(),
-      GTK_RESPONSE_ACCEPT);
+  if (prompt.HasAcceptButtonLabel()) {
+    gtk_dialog_add_button(
+        GTK_DIALOG(dialog_),
+        UTF16ToUTF8(prompt.GetAcceptButtonLabel()).c_str(),
+        GTK_RESPONSE_ACCEPT);
+  }
 #if !GTK_CHECK_VERSION(2, 22, 0)
   gtk_dialog_set_has_separator(GTK_DIALOG(dialog_), FALSE);
 #endif
 
   GtkWidget* content_area = gtk_dialog_get_content_area(GTK_DIALOG(dialog_));
   gtk_box_set_spacing(GTK_BOX(content_area), ui::kContentAreaSpacing);
 
   // Divide the dialog vertically (item data and icon on the top, permissions
   // on the bottom).
   GtkWidget* content_vbox = gtk_vbox_new(FALSE, ui::kControlSpacing);
@@ skipping 248 matching lines @@
   new chrome::ExtensionInstallDialog(show_params, delegate, prompt);
 }
 
 }  // namespace
 
 // static
 ExtensionInstallPrompt::ShowDialogCallback
 ExtensionInstallPrompt::GetDefaultShowDialogCallback() {
   return base::Bind(&ShowExtensionInstallDialogImpl);
 }