Get rid of most instance of 'foo != NULL'

core/src/fxcrt/fx_xml_parser.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 "xml_int.h"
 
 #include "core/include/fxcrt/fx_ext.h"
 #include "core/include/fxcrt/fx_xml.h"
@@ skipping 801 matching lines @@
         item.m_AttrName == name) {
       m_pMap->RemoveAt(i);
       return;
     }
   }
 }
 int CXML_AttrMap::GetSize() const {
   return m_pMap == NULL ? 0 : m_pMap->GetSize();
 }
 CXML_AttrItem& CXML_AttrMap::GetAt(int index) const {
-  ASSERT(m_pMap != NULL);
   return (*m_pMap)[index];
 }
 void CXML_AttrMap::RemoveAll() {
   if (!m_pMap) {
     return;
   }
   m_pMap->RemoveAll();
   delete m_pMap;
   m_pMap = NULL;
 }