THRIFT-5225: Use nullptr instead of NULL
Patch: Zezeng Wang

This closes #2168
diff --git a/contrib/fb303/cpp/FacebookBase.h b/contrib/fb303/cpp/FacebookBase.h
index daa5246..e0be4bf 100644
--- a/contrib/fb303/cpp/FacebookBase.h
+++ b/contrib/fb303/cpp/FacebookBase.h
@@ -65,7 +65,7 @@
   virtual void reinitialize() {}
 
   virtual void shutdown() {
-    if (server_.get() != NULL) {
+    if (server_.get() != nullptr) {
       server_->stop();
     }
   }