Fix NULL pointer dereference in CPDF_InterForm.

core/include/fpdfdoc/fpdf_doc.h

 // 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
 
 #ifndef CORE_INCLUDE_FPDFDOC_FPDF_DOC_H_
 #define CORE_INCLUDE_FPDFDOC_FPDF_DOC_H_
 
 #include <map>
@@ skipping 720 matching lines @@
                             int iType,
                             const CPDF_FormField* pExcludedField,
                             const CPDF_FormControl* pExcludedControl);
 
   int CompareFieldName(const CFX_WideString& name1,
                        const CFX_WideString& name2);
 
   int CompareFieldName(const CFX_ByteString& name1,
                        const CFX_ByteString& name2);
 
-  CPDF_Document* m_pDocument;
+  CPDF_Document* const m_pDocument;
 
   FX_BOOL m_bGenerateAP;
 
   CPDF_Dictionary* m_pFormDict;
 
   std::map<const CPDF_Dictionary*, CPDF_FormControl*> m_ControlMap;
 
-  CFieldTree* m_pFieldTree;
+  nonstd::unique_ptr<CFieldTree> m_pFieldTree;
 
   CFX_ByteString m_bsEncoding;
 
   CPDF_FormNotify* m_pFormNotify;
 
   FX_BOOL m_bUpdated;
   friend class CPDF_FormControl;
   friend class CPDF_FormField;
 };
 #define FORMFIELD_READONLY 0x01
@@ skipping 440 matching lines @@
                         FX_FLOAT fc[4],
                         const CFX_ByteStringC& csEntry);
 
   CFX_WideString GetCaption(const CFX_ByteStringC& csEntry);
 
   CPDF_Stream* GetIcon(const CFX_ByteStringC& csEntry);
   friend class CPDF_FormControl;
 };
 
 #endif  // CORE_INCLUDE_FPDFDOC_FPDF_DOC_H_