Fix some return FALSE in functions that return pointers

xfa/fxfa/parser/cxfa_simple_parser.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_simple_parser.h"
 
 #include "core/fxcrt/fx_ext.h"
 #include "xfa/fgas/crt/fgas_codepage.h"
@@ skipping 19 matching lines @@
       continue;
 
     if (!bVerifyWellFormness)
       return pXMLNode;
 
     for (CFDE_XMLNode* pNextNode =
              pXMLNode->GetNodeItem(CFDE_XMLNode::NextSibling);
          pNextNode;
          pNextNode = pNextNode->GetNodeItem(CFDE_XMLNode::NextSibling)) {
       if (pNextNode->GetType() == FDE_XMLNODE_Element)
-        return FALSE;
+        return nullptr;
     }
     return pXMLNode;
   }
   return nullptr;
 }
 
 void GetElementTagNamespaceURI(CFDE_XMLElement* pElement,
                                CFX_WideString& wsNamespaceURI) {
   CFX_WideString wsNodeStr;
   pElement->GetNamespacePrefix(wsNodeStr);
@@ skipping 1249 matching lines @@
         pXFANode->GetDocument()->SetFlag(XFA_DOCFLAG_StrictScoping, TRUE);
       }
     }
   }
 }
 
 void CXFA_SimpleParser::CloseParser() {
   m_pXMLDoc.reset();
   m_pStream.reset();
 }