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)