async_hooks: CHECK that resource is not empty

This condition can be triggered through the public C++ embedder API.

PR-URL: https://github.com/nodejs/node/pull/14694
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

src/async-wrap.cc

@@ -645,6 +645,8 @@ void AsyncWrap::EmitAsyncInit(Environment* env,
                               Local<String> type,
                               double async_id,
                               double trigger_id) {
+  CHECK(!object.IsEmpty());
+  CHECK(!type.IsEmpty());
   AsyncHooks* async_hooks = env->async_hooks();
 
   // Nothing to execute, so can continue normally.