Get rid of NULLs in fpdfsdk/

fpdfsdk/pdfwindow/PWL_Caret.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 FPDFSDK_PDFWINDOW_PWL_CARET_H_
 #define FPDFSDK_PDFWINDOW_PWL_CARET_H_
 
 #include "fpdfsdk/pdfwindow/PWL_Wnd.h"
@@ skipping 10 matching lines @@
 class CPWL_Caret : public CPWL_Wnd {
  public:
   CPWL_Caret();
   ~CPWL_Caret() override;
 
   // CPWL_Wnd
   CFX_ByteString GetClassName() const override;
   void GetThisAppearanceStream(CFX_ByteTextBuf& sAppStream) override;
   void DrawThisAppearance(CFX_RenderDevice* pDevice,
                           CFX_Matrix* pUser2Device) override;
-  void InvalidateRect(CFX_FloatRect* pRect = NULL) override;
+  void InvalidateRect(CFX_FloatRect* pRect = nullptr) override;
   void SetVisible(FX_BOOL bVisible) override {}
   void TimerProc() override;
 
   void SetCaret(FX_BOOL bVisible,
                 const CFX_FloatPoint& ptHead,
                 const CFX_FloatPoint& ptFoot);
   CFX_ByteString GetCaretAppearanceStream(const CFX_FloatPoint& ptOffset);
   void SetInvalidRect(CFX_FloatRect rc) { m_rcInvalid = rc; }
 
  private:
   void GetCaretApp(CFX_ByteTextBuf& sAppStream, const CFX_FloatPoint& ptOffset);
   CFX_FloatRect GetCaretRect() const;
 
   FX_BOOL m_bFlash;
   CFX_FloatPoint m_ptHead;
   CFX_FloatPoint m_ptFoot;
   FX_FLOAT m_fWidth;
   int32_t m_nDelay;
   CFX_FloatRect m_rcInvalid;
 };
 
 #endif  // FPDFSDK_PDFWINDOW_PWL_CARET_H_