Get rid of NULLs in core/

core/fxcodec/lgif/fx_gif.h

 // 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
 
 #ifndef CORE_FXCODEC_LGIF_FX_GIF_H_
 #define CORE_FXCODEC_LGIF_FX_GIF_H_
 
 #include <setjmp.h>
@@ skipping 100 matching lines @@
   GifGCE* gce_ptr;
   GifPTE* pte_ptr;
   CFX_ByteString* string_ptr;
 } GifPlainText;
 class CGifLZWDecoder {
  public:
   struct tag_Table {
     uint16_t prefix;
     uint8_t suffix;
   };
-  CGifLZWDecoder(FX_CHAR* error_ptr = NULL) { err_msg_ptr = error_ptr; }
+  CGifLZWDecoder(FX_CHAR* error_ptr = nullptr) { err_msg_ptr = error_ptr; }
   void InitTable(uint8_t code_len);
 
   int32_t Decode(uint8_t* des_buf, uint32_t& des_size);
 
   void Input(uint8_t* src_buf, uint32_t src_size);
   uint32_t GetAvailInput();
 
  private:
   void ClearTable();
   void AddCode(uint16_t prefix_code, uint8_t append_char);
@@ skipping 155 matching lines @@
                       uint8_t* src_buf,
                       uint32_t src_size);
 uint32_t gif_get_avail_input(gif_decompress_struct_p gif_ptr,
                              uint8_t** avial_buf_ptr);
 void interlace_buf(const uint8_t* buf, uint32_t width, uint32_t height);
 FX_BOOL gif_encode(gif_compress_struct_p gif_ptr,
                    uint8_t*& dst_buf,
                    uint32_t& dst_len);
 
 #endif  // CORE_FXCODEC_LGIF_FX_GIF_H_