src: replace NULL with nullptr

Now that we are building with C++11 features enabled, replace use
of NULL with nullptr.

The benefit of using nullptr is that it can never be confused for
an integral type because it does not support implicit conversions
to integral types except boolean - unlike NULL, which is defined
as a literal `0`.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/tls_wrap.h b/src/tls_wrap.h
index b12a6b6612..598288c621 100644
--- a/src/tls_wrap.h
+++ b/src/tls_wrap.h
@@ -89,8 +89,8 @@ class TLSCallbacks : public crypto::SSLWrap<TLSCallbacks>,
     WriteItem(WriteWrap* w, uv_write_cb cb) : w_(w), cb_(cb) {
     }
     ~WriteItem() {
-      w_ = NULL;
-      cb_ = NULL;
+      w_ = nullptr;
+      cb_ = nullptr;
     }
 
     WriteWrap* w_;