Remove NULL in xfa/

xfa/fwl/basewidget/fwl_formproxyimp.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "xfa/fwl/basewidget/fwl_formproxyimp.h"
 
 #include "xfa/fwl/core/fwl_formimp.h"
 #include "xfa/fwl/core/fwl_noteimp.h"
@@ skipping 36 matching lines @@
 }
 FWL_Error CFWL_FormProxyImp::DrawWidget(CFX_Graphics* pGraphics,
                                         const CFX_Matrix* pMatrix) {
   return FWL_Error::Succeeded;
 }
 
 CFWL_FormProxyImpDelegate::CFWL_FormProxyImpDelegate(CFWL_FormProxyImp* pOwner)
     : m_pOwner(pOwner) {}
 
 void CFWL_FormProxyImpDelegate::OnProcessMessage(CFWL_Message* pMessage) {
-  IFWL_WidgetDelegate* pDelegate = m_pOwner->m_pOuter->SetDelegate(NULL);
+  IFWL_WidgetDelegate* pDelegate = m_pOwner->m_pOuter->SetDelegate(nullptr);
   pDelegate->OnProcessMessage(pMessage);
 }