Get rid of NULLs in xfa/fxbarcode/

xfa/fxbarcode/common/BC_CommonCharacterSetECI.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
 // Original code is licensed as follows:
 /*
  * Copyright 2008 ZXing authors
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ skipping 18 matching lines @@
     CFX_ByteString encodingName)
     : CBC_CommonECI(value), m_encodingName(encodingName) {}
 CBC_CommonCharacterSetECI::~CBC_CommonCharacterSetECI() {}
 CFX_ByteString CBC_CommonCharacterSetECI::GetEncodingName() {
   return m_encodingName;
 }
 void CBC_CommonCharacterSetECI::AddCharacterSet(int32_t value,
                                                 CFX_ByteString encodingName) {}
 CBC_CommonCharacterSetECI* CBC_CommonCharacterSetECI::GetCharacterSetECIByValue(
     int32_t value) {
-  return NULL;
+  return nullptr;
 }
 CBC_CommonCharacterSetECI* CBC_CommonCharacterSetECI::GetCharacterSetECIByName(
     const CFX_ByteString& name) {
-  return NULL;
+  return nullptr;
 }