fix worker termination in example (github issue bellard#98)

Author: Fabrice Bellard

tests/test_worker_module.js

@@ -10,6 +10,7 @@ function handle_msg(e) {
  switch(ev.type) {
  case "abort":
  parent.postMessage({ type: "done" });
+ parent.onMessage = null; /* terminate the worker */
  break;
  case "sab":
  /* modify the SharedArrayBuffer */