test: fix compiler warning in n-api test

Missed in ca786c3734. This does
not actually affect the outcome because returning `nullptr` or
`this` from a constructor has the same effect.

PR-URL: https://github.com/nodejs/node/pull/12318
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

test/addons-napi/test_constructor/test_constructor.c

@@ -40,7 +40,7 @@ napi_value Echo(napi_env env, napi_callback_info info) {
 
 napi_value New(napi_env env, napi_callback_info info) {
   napi_value _this;
-  NAPI_CALL(env, napi_get_cb_info(env, info, NULL, NULL, NULL, &_this));
+  NAPI_CALL(env, napi_get_cb_info(env, info, NULL, NULL, &_this, NULL));
 
   return _this;
 }