n-api: use nullptr instead of NULL in node_api.cc

This commit changes two checks which use NULL to use nullptr.

I'm not very familiar with N-API but wanted to bring this up in case
it was something that was overlooked.

Backport-PR-URL: #19447
PR-URL: #17276
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Lance Ball <lball@redhat.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: MichaëZasso <targos@protonmail.com>

src/node_api.cc

@@ -1228,7 +1228,7 @@ napi_status napi_delete_property(napi_env env,
   v8::Maybe<bool> delete_maybe = obj->Delete(context, k);
   CHECK_MAYBE_NOTHING(env, delete_maybe, napi_generic_failure);
 
-  if (result != NULL)
+  if (result != nullptr)
     *result = delete_maybe.FromMaybe(false);
 
   return GET_RETURN_STATUS(env);
@@ -1406,7 +1406,7 @@ napi_status napi_delete_element(napi_env env,
   v8::Maybe<bool> delete_maybe = obj->Delete(context, index);
   CHECK_MAYBE_NOTHING(env, delete_maybe, napi_generic_failure);
 
-  if (result != NULL)
+  if (result != nullptr)
     *result = delete_maybe.FromMaybe(false);
 
   return GET_RETURN_STATUS(env);