Remove "this==NULL" and adjust corresponding callers

core/src/fpdfdoc/doc_basic.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 "../../include/fpdfdoc/fpdf_doc.h"
 const int nMaxRecursion = 32;
 int CPDF_Dest::GetPageIndex(CPDF_Document* pDoc)
 {
@@ skipping 54 matching lines @@
 }
 CFX_ByteString CPDF_Dest::GetRemoteName()
 {
     if (m_pObj == NULL) {
         return CFX_ByteString();
     }
     return m_pObj->GetString();
 }
 CPDF_NameTree::CPDF_NameTree(CPDF_Document* pDoc, FX_BSTR category)
 {
-    m_pRoot = pDoc->GetRoot()->GetDict(FX_BSTRC("Names"))->GetDict(category);
+    if (pDoc->GetRoot() && pDoc->GetRoot()->GetDict(FX_BSTRC("Names")))
+        m_pRoot = pDoc->GetRoot()->GetDict(FX_BSTRC("Names"))->GetDict(category);
+    else
+        m_pRoot = NULL;
 }
 static CPDF_Object* SearchNameNode(CPDF_Dictionary* pNode, const CFX_ByteString& csName,
                                    int& nIndex, CPDF_Array** ppFind, int nLevel = 0)
 {
     if (nLevel > nMaxRecursion) {
         return NULL;
     }
     CPDF_Array* pLimits = pNode->GetArray(FX_BSTRC("Limits"));
     if (pLimits != NULL) {
         CFX_ByteString csLeft = pLimits->GetString(0);
@@ skipping 472 matching lines @@
     if (nPage > 0 && nPage <= nPages) {
         return nPage;
     }
     return -1;
 }
 FX_INT32 CPDF_PageLabel::GetPageByLabel(FX_WSTR wsLabel) const
 {
     CFX_ByteString bsLabel = PDF_EncodeText((CFX_WideString)wsLabel);
     return GetPageByLabel(bsLabel);
 }