Null CPDF_CountedObj::m_pObj prior to deletion

core/fpdfapi/fpdf_page/cpdf_countedobject.h

 // 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
 
 #ifndef CORE_FPDFAPI_FPDF_PAGE_CPDF_COUNTEDOBJECT_H_
 #define CORE_FPDFAPI_FPDF_PAGE_CPDF_COUNTEDOBJECT_H_
 
 #include "core/fpdfapi/fpdf_page/cpdf_pattern.h"
 #include "core/fpdfapi/fpdf_page/include/cpdf_colorspace.h"
 #include "core/fxcrt/include/fx_system.h"
 
 template <class T>
 class CPDF_CountedObject {
  public:
   explicit CPDF_CountedObject(T* ptr) : m_nCount(1), m_pObj(ptr) {}
   void reset(T* ptr) {  // CAUTION: tosses prior ref counts.
     m_nCount = 1;
     m_pObj = ptr;
   }
   void clear() {  // Now you're all weak ptrs ...
-    delete m_pObj;
+    // Guard against accidental re-entry.
+    T* pObj = m_pObj;
     m_pObj = nullptr;
+    delete pObj;
   }
   T* get() const { return m_pObj; }
   T* AddRef() {
     ASSERT(m_pObj);
     ++m_nCount;
     return m_pObj;
   }
   void RemoveRef() {
     if (m_nCount)
       --m_nCount;
   }
   size_t use_count() const { return m_nCount; }
 
  protected:
   size_t m_nCount;
   T* m_pObj;
 };
 using CPDF_CountedColorSpace = CPDF_CountedObject<CPDF_ColorSpace>;
 using CPDF_CountedPattern = CPDF_CountedObject<CPDF_Pattern>;
 
 #endif  // CORE_FPDFAPI_FPDF_PAGE_CPDF_COUNTEDOBJECT_H_