Fix cluster-fuzz regression when getting message from Worker

test/mjsunit/d8-worker.js

Index: test/mjsunit/d8-worker.js
diff --git a/test/mjsunit/d8-worker.js b/test/mjsunit/d8-worker.js
index 807791717e1f6f7f047a9cc718468ad4f138a176..ef02ca5b405815ca5252886b4cfe46d4ead4dfbc 100644
--- a/test/mjsunit/d8-worker.js
+++ b/test/mjsunit/d8-worker.js
@@ -128,4 +128,12 @@ if (this.Worker) {
   assertEquals("DONE", w.getMessage());
 
   w.terminate();
+
+
+  // Make sure that the main thread doesn't block forever in getMessage() if
+  // the worker dies without posting a message.
+  function f2() {}
+  var w2 = new Worker(f2);
+  var msg = w2.getMessage();
+  assertEquals(undefined, msg);
 }