Get rid of NULLs in core/

xfa/fxfa/parser/cxfa_widgetdata.cpp

 // Copyright 2016 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/fxfa/parser/cxfa_widgetdata.h"
 
 #include "core/fxcrt/include/fx_ext.h"
 #include "xfa/fxbarcode/include/BC_Library.h"
@@ skipping 1053 matching lines @@
   if (!pUIChild)
     return -1;
   if (CXFA_Node* pNode = pUIChild->GetChild(0, XFA_ELEMENT_Comb))
     return pNode->GetInteger(XFA_ATTRIBUTE_NumberOfCells);
   return -1;
 }
 
 CFX_WideString CXFA_WidgetData::GetBarcodeType() {
   CXFA_Node* pUIChild = GetUIChild();
   return pUIChild ? CFX_WideString(pUIChild->GetCData(XFA_ATTRIBUTE_Type))
-                  : nullptr;
+                  : CFX_WideString();
 }
 
 FX_BOOL CXFA_WidgetData::GetBarcodeAttribute_CharEncoding(int32_t& val) {
   CXFA_Node* pUIChild = GetUIChild();
   CFX_WideString wsCharEncoding;
   if (pUIChild->TryCData(XFA_ATTRIBUTE_CharEncoding, wsCharEncoding)) {
     if (wsCharEncoding.CompareNoCase(L"UTF-16")) {
       val = CHAR_ENCODING_UNICODE;
       return TRUE;
     }
@@ skipping 694 matching lines @@
         }
       }
     } else if (wc == L'.') {
       iTread_ = 0;
       iLead = -1;
     }
     wsRet += wc;
   }
   return wsRet;
 }