Get rid of NULLs in fpdfsdk/

Review-Url: https://codereview.chromium.org/2031653003
diff --git a/fpdfsdk/javascript/JS_Object.cpp b/fpdfsdk/javascript/JS_Object.cpp
index 7dc91a7..6339bb7 100644
--- a/fpdfsdk/javascript/JS_Object.cpp
+++ b/fpdfsdk/javascript/JS_Object.cpp
@@ -31,7 +31,7 @@
 CJS_EmbedObj::CJS_EmbedObj(CJS_Object* pJSObject) : m_pJSObject(pJSObject) {}
 
 CJS_EmbedObj::~CJS_EmbedObj() {
-  m_pJSObject = NULL;
+  m_pJSObject = nullptr;
 }
 
 int CJS_EmbedObj::MsgBox(CPDFDoc_Environment* pApp,
@@ -87,7 +87,7 @@
   if (pContext->IsMsgBoxEnabled()) {
     CPDFDoc_Environment* pApp = pContext->GetReaderApp();
     if (pApp)
-      pApp->JS_appAlert(swMsg, NULL, 0, 3);
+      pApp->JS_appAlert(swMsg, nullptr, 0, 3);
   }
 }