Map in LookUpGlyphBitmap even when unsuccessful

core/fxge/ge/cfx_facecache.cpp

 // Copyright 2016 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 "core/fxge/include/cfx_facecache.h"
 
 #include <algorithm>
 
@@ skipping 368 matching lines @@
     m_SizeMap[FaceGlyphsKey] = std::unique_ptr<CFX_SizeGlyphCache>(pSizeCache);
   } else {
     pSizeCache = it->second.get();
   }
   auto it2 = pSizeCache->m_GlyphMap.find(glyph_index);
   if (it2 != pSizeCache->m_GlyphMap.end())
     return it2->second;
 
   CFX_GlyphBitmap* pGlyphBitmap = RenderGlyph(pFont, glyph_index, bFontStyle,
                                               pMatrix, dest_width, anti_alias);
-  if (!pGlyphBitmap)
-    return nullptr;
-
   pSizeCache->m_GlyphMap[glyph_index] = pGlyphBitmap;
   return pGlyphBitmap;
 }