CPDF_Document::LoadPattern() and friends always have a valid matrix.

core/fpdfapi/fpdf_page/cpdf_tilingpattern.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/fpdf_page/cpdf_tilingpattern.h"
 
 #include "core/fpdfapi/fpdf_page/include/cpdf_form.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_dictionary.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_object.h"
 #include "core/fpdfapi/fpdf_parser/include/cpdf_stream.h"
 
 CPDF_TilingPattern::CPDF_TilingPattern(CPDF_Document* pDoc,
                                        CPDF_Object* pPatternObj,
-                                       const CFX_Matrix* parentMatrix)
+                                       const CFX_Matrix& parentMatrix)
     : CPDF_Pattern(TILING, pDoc, pPatternObj, parentMatrix) {
   CPDF_Dictionary* pDict = m_pPatternObj->GetDict();
   m_Pattern2Form = pDict->GetMatrixBy("Matrix");
   m_bColored = pDict->GetIntegerBy("PaintType") == 1;
-  if (parentMatrix)
-    m_Pattern2Form.Concat(*parentMatrix);
+  m_Pattern2Form.Concat(parentMatrix);
 }
 
 CPDF_TilingPattern::~CPDF_TilingPattern() {
 }
 
 FX_BOOL CPDF_TilingPattern::Load() {
   if (m_pForm)
     return TRUE;
 
   CPDF_Dictionary* pDict = m_pPatternObj->GetDict();
   if (!pDict)
     return FALSE;
 
   m_bColored = pDict->GetIntegerBy("PaintType") == 1;
   m_XStep = (FX_FLOAT)FXSYS_fabs(pDict->GetNumberBy("XStep"));
   m_YStep = (FX_FLOAT)FXSYS_fabs(pDict->GetNumberBy("YStep"));
 
   CPDF_Stream* pStream = m_pPatternObj->AsStream();
   if (!pStream)
     return FALSE;
 
   m_pForm.reset(new CPDF_Form(m_pDocument, nullptr, pStream));
   m_pForm->ParseContent(nullptr, &m_ParentMatrix, nullptr);
   m_BBox = pDict->GetRectBy("BBox");
   return TRUE;
 }