Fix failures after removing FX_BSTRC.

core/src/fxcrt/fx_basic_wstring.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 <stddef.h>  // For offsetof().
 #include <cctype>
 
 #include "core/include/fxcrt/fx_basic.h"
@@ skipping 270 matching lines @@
   if (m_pData == NULL) {
     return (lpsz == NULL || lpsz[0] == 0) ? 0 : -1;
   }
   return FXSYS_wcscmp(m_pData->m_String, lpsz);
 }
 CFX_ByteString CFX_WideString::UTF8Encode() const {
   return FX_UTF8Encode(*this);
 }
 CFX_ByteString CFX_WideString::UTF16LE_Encode() const {
   if (m_pData == NULL) {
-    return CFX_ByteString("\0\0");
+    return CFX_ByteString("\0\0", 2);
   }
   int len = m_pData->m_nDataLength;
   CFX_ByteString result;
   FX_CHAR* buffer = result.GetBuffer(len * 2 + 2);
   for (int i = 0; i < len; i++) {
     buffer[i * 2] = m_pData->m_String[i] & 0xff;
     buffer[i * 2 + 1] = m_pData->m_String[i] >> 8;
   }
   buffer[len * 2] = 0;
   buffer[len * 2 + 1] = 0;
@@ skipping 757 matching lines @@
       return (CFX_CharMap*)&g_DefaultJISMapper;
     case 936:
       return (CFX_CharMap*)&g_DefaultGBKMapper;
     case 949:
       return (CFX_CharMap*)&g_DefaultUHCMapper;
     case 950:
       return (CFX_CharMap*)&g_DefaultBig5Mapper;
   }
   return NULL;
 }