Get rid of NULLs in core/

core/fxcrt/include/fx_ext.h

Index: core/fxcrt/include/fx_ext.h
diff --git a/core/fxcrt/include/fx_ext.h b/core/fxcrt/include/fx_ext.h
index b6c05ae9bcb58d95160617953af530f2983aed8e..d37db67d4ab49d21c8a996d505eb2b8286bc7434 100644
--- a/core/fxcrt/include/fx_ext.h
+++ b/core/fxcrt/include/fx_ext.h
@@ -24,10 +24,10 @@ FX_FLOAT FXSYS_tan(FX_FLOAT a);
 FX_FLOAT FXSYS_logb(FX_FLOAT b, FX_FLOAT x);
 FX_FLOAT FXSYS_strtof(const FX_CHAR* pcsStr,
                       int32_t iLength = -1,
-                      int32_t* pUsedLen = NULL);
+                      int32_t* pUsedLen = nullptr);
 FX_FLOAT FXSYS_wcstof(const FX_WCHAR* pwsStr,
                       int32_t iLength = -1,
-                      int32_t* pUsedLen = NULL);
+                      int32_t* pUsedLen = nullptr);
 FX_WCHAR* FXSYS_wcsncpy(FX_WCHAR* dstStr, const FX_WCHAR* srcStr, size_t count);
 int32_t FXSYS_wcsnicmp(const FX_WCHAR* s1, const FX_WCHAR* s2, size_t count);
 int32_t FXSYS_strnicmp(const FX_CHAR* s1, const FX_CHAR* s2, size_t count);