Remove NULL in xfa/

xfa/fgas/font/fgas_fontutils.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/fgas/font/fgas_fontutils.h"
 
 #include "core/fxcrt/include/fx_ext.h"
 #include "xfa/fgas/font/fgas_font.h"
@@ skipping 131 matching lines @@
     iMid = (iStart + iEnd) / 2;
     const FGAS_FONTUSB& usb = g_FXGdiFontUSBTable[iMid];
     if (wUnicode < usb.wStartUnicode) {
       iEnd = iMid - 1;
     } else if (wUnicode > usb.wEndUnicode) {
       iStart = iMid + 1;
     } else {
       return &usb;
     }
   } while (iStart <= iEnd);
-  return NULL;
+  return nullptr;
 }