Fixed crash on NULL de-referencing.

core/src/fpdftext/fpdf_text_int.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/fpdfapi/fpdf_resource.h"
 #include "../../include/fpdfapi/fpdf_pageobj.h"
 #include "../../include/fpdftext/fpdf_text.h"
 #include "../../include/fpdfapi/fpdf_page.h"
@@ skipping 1481 matching lines @@
     if (nContentMark < 1) {
         return;
     }
     CFX_WideString actText;
     CPDF_Dictionary* pDict = NULL;
     int n = 0;
     for (n = 0; n < nContentMark; n++) {
         CPDF_ContentMarkItem& item = pMarkData->GetItem(n);
         CFX_ByteString tagStr = (CFX_ByteString)item.GetName();
         pDict = (CPDF_Dictionary*)item.GetParam();
-        CPDF_String* temp = (CPDF_String*)pDict->GetElement(FX_BSTRC("ActualText"));
+        CPDF_String* temp = (CPDF_String*)(pDict ? pDict->GetElement(FX_BSTRC("ActualText")) : NULL);
         if (temp) {
             actText = temp->GetUnicodeText();
         }
     }
     FX_STRSIZE nItems = actText.GetLength();
     if (nItems < 1) {
         return;
     }
     CPDF_Font*  pFont = pTextObj->GetFont();
     CFX_AffineMatrix formMatrix = Obj.m_formMatrix;
@@ skipping 1335 matching lines @@
     if (!m_IsParserd || index < 0 || index >= m_LinkList.GetSize()) {
         return;
     }
     CPDF_LinkExt* link = NULL;
     link = m_LinkList.GetAt(index);
     if (!link) {
         return ;
     }
     m_pTextPage->GetRectArray(link->m_Start, link->m_Count, rects);
 }