Revert "Remove FX_Alloc() null checks now that it can't return NULL."

core/src/fxcrt/fx_basic_maps.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/fxcrt/fx_ext.h"
 #include "plex.h"
 static void ConstructElement(CFX_ByteString* pNewData)
 {
@@ skipping 395 matching lines @@
 {
     if (len < (int)sizeof(_CompactString)) {
         pCompact->m_CompactLen = (FX_BYTE)len;
         FXSYS_memcpy32(&pCompact->m_LenHigh, pStr, len);
         return;
     }
     pCompact->m_CompactLen = 0xff;
     pCompact->m_LenHigh = len / 256;
     pCompact->m_LenLow = len % 256;
     pCompact->m_pBuffer = FX_Alloc(FX_BYTE, len);
-    FXSYS_memcpy32(pCompact->m_pBuffer, pStr, len);
+    if (pCompact->m_pBuffer) {
+        FXSYS_memcpy32(pCompact->m_pBuffer, pStr, len);
+    }
 }
 static CFX_ByteStringC _CompactStringGet(_CompactString* pCompact)
 {
     if (pCompact->m_CompactLen == 0xff) {
         return CFX_ByteStringC(pCompact->m_pBuffer, pCompact->m_LenHigh * 256 + pCompact->m_LenLow);
     }
     if (pCompact->m_CompactLen == 0xfe) {
         return CFX_ByteStringC();
     }
     return CFX_ByteStringC(&pCompact->m_LenHigh, pCompact->m_CompactLen);
@@ skipping 205 matching lines @@
             buf[mid].value = value;
             return;
         }
     }
     m_Buffer.InsertBlock(low * sizeof(_DWordPair), &pair, sizeof(_DWordPair));
 }
 void CFX_CMapDWordToDWord::EstimateSize(FX_DWORD size, FX_DWORD grow_by)
 {
     m_Buffer.EstimateSize(size, grow_by);
 }