Assert objnum non-zero in ReplaceIndirectObjectIfHigherGeneration()

core/fpdfapi/parser/cpdf_indirect_object_holder.cpp

 // 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
 
 #include "core/fpdfapi/parser/cpdf_indirect_object_holder.h"
 
 #include "core/fpdfapi/parser/cpdf_object.h"
 #include "core/fpdfapi/parser/cpdf_parser.h"
@@ skipping 38 matching lines @@
   m_LastObjNum++;
   m_IndirectObjs[m_LastObjNum].release();  // TODO(tsepez): stop this leak.
   m_IndirectObjs[m_LastObjNum].reset(pObj);
   pObj->m_ObjNum = m_LastObjNum;
   return m_LastObjNum;
 }
 
 bool CPDF_IndirectObjectHolder::ReplaceIndirectObjectIfHigherGeneration(
     uint32_t objnum,
     CPDF_Object* pObj) {
-  if (!objnum || !pObj)
+  ASSERT(objnum);
+  if (!pObj)
     return false;
 
   CPDF_Object* pOldObj = GetIndirectObject(objnum);
   if (pOldObj && pObj->GetGenNum() <= pOldObj->GetGenNum()) {
     delete pObj;
     return false;
   }
   pObj->m_ObjNum = objnum;
   m_IndirectObjs[objnum].reset(pObj);
   m_LastObjNum = std::max(m_LastObjNum, objnum);
   return true;
 }
 
 void CPDF_IndirectObjectHolder::ReleaseIndirectObject(uint32_t objnum) {
   CPDF_Object* pObj = GetIndirectObject(objnum);
   if (!pObj || pObj->GetObjNum() == CPDF_Object::kInvalidObjNum)
     return;
 
   m_IndirectObjs.erase(objnum);
 }