Take advantage of implicit std::unique_ptr<>(nulltpr_t) ctor.

core/fpdfapi/page/fpdf_page_func.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 "core/fpdfapi/page/pageint.h"
 
 #include <limits.h>
 
@@ skipping 733 matching lines @@
   if (type == Type::kType0Sampled)
     pFunc.reset(new CPDF_SampledFunc());
   else if (type == Type::kType2ExpotentialInterpolation)
     pFunc.reset(new CPDF_ExpIntFunc());
   else if (type == Type::kType3Stitching)
     pFunc.reset(new CPDF_StitchFunc());
   else if (type == Type::kType4PostScript)
     pFunc.reset(new CPDF_PSFunc());
 
   if (!pFunc || !pFunc->Init(pFuncObj))
-    return std::unique_ptr<CPDF_Function>();
+    return nullptr;
+
   return pFunc;
 }
 
 // static
 CPDF_Function::Type CPDF_Function::IntegerToFunctionType(int iType) {
   switch (iType) {
     case 0:
     case 2:
     case 3:
     case 4:
@@ skipping 84 matching lines @@
   return m_Type == Type::kType2ExpotentialInterpolation
              ? static_cast<const CPDF_ExpIntFunc*>(this)
              : nullptr;
 }
 
 const CPDF_StitchFunc* CPDF_Function::ToStitchFunc() const {
   return m_Type == Type::kType3Stitching
              ? static_cast<const CPDF_StitchFunc*>(this)
              : nullptr;
 }