No executionListeners? Error message was: Exception occurred: class ptolemy.actor.NoTokenException(No token to return.
  in .topLevel.act2.input)
ptolemy.actor.NoTokenException: No token to return.
  in .topLevel.act2.input
	at ptolemy.actor.IOPort.get(IOPort.java:1005)
	at ptolemy.actor.process.test.ProcessSink.fire(ProcessSink.java:74)
	at ptolemy.actor.process.ProcessThread._iterateActor(ProcessThread.java:339)
	at ptolemy.actor.process.ProcessThread.run(ProcessThread.java:213)