Get rid of NULLs in core/

core/fxcrt/xml_int.h

Index: core/fxcrt/xml_int.h
diff --git a/core/fxcrt/xml_int.h b/core/fxcrt/xml_int.h
index 864b4e8789bd8de34f8417de25530e5e35c2fd23..6d3db4f52598d39ac2dedbbcabf1e0c34b0da101 100644
--- a/core/fxcrt/xml_int.h
+++ b/core/fxcrt/xml_int.h
@@ -48,7 +48,7 @@ class CXML_DataBufAcc : public IFX_BufferRead {
 class CXML_DataStmAcc : public IFX_BufferRead {
  public:
   explicit CXML_DataStmAcc(IFX_FileRead* pFileRead)
-      : m_pFileRead(pFileRead), m_pBuffer(NULL), m_nStart(0), m_dwSize(0) {
+      : m_pFileRead(pFileRead), m_pBuffer(nullptr), m_nStart(0), m_dwSize(0) {
     ASSERT(m_pFileRead);
   }
   ~CXML_DataStmAcc() override { FX_Free(m_pBuffer); }