Error During Simulation

I have an error that's driving my crazy. I have attempted to attach the file so others may try it and see if the same happens for them. Though I have had problems in the past with attaching Alice files so it might not work entirely correctly.

I have something set up so when I press the up arrow my character will move forward while performing the walk animation to make it look more realistic. When I let go of the up arrow key the simulation closes and I get something like this:

Error during simulation.


Alice version: 2.2 6/10/2009

Throwable that caused the error:
java.lang.NullPointerException
at edu.cmu.cs.stage3.alice.core.Behavior$RuntimeStack .pop(Behavior.java:49)
at edu.cmu.cs.stage3.alice.core.Behavior.popStack(Beh avior.java:360)
at edu.cmu.cs.stage3.alice.core.response.LoopNInOrder $RuntimeLoopNInOrder.epilogue(LoopNInOrder.java:10 2)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.childrenEpiloguesIf Necessary(CompositeResponse.java:67)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.epilogue(CompositeR esponse.java:73)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.childrenEpiloguesIf Necessary(CompositeResponse.java:67)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.epilogue(CompositeR esponse.java:73)
at edu.cmu.cs.stage3.alice.core.response.CallToUserDe finedResponse$RuntimeCallToUserDefinedResponse.epi logue(CallToUserDefinedResponse.java:94)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.childrenEpiloguesIf Necessary(CompositeResponse.java:67)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.epilogue(CompositeR esponse.java:73)
at edu.cmu.cs.stage3.alice.core.response.LoopNInOrder $RuntimeLoopNInOrder.epilogue(LoopNInOrder.java:99 )
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.childrenEpiloguesIf Necessary(CompositeResponse.java:67)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.epilogue(CompositeR esponse.java:73)
at edu.cmu.cs.stage3.alice.core.response.DoTogether$R untimeDoTogether.epilogue(DoTogether.java:81)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.childrenEpiloguesIf Necessary(CompositeResponse.java:67)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.epilogue(CompositeR esponse.java:73)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.childrenEpiloguesIf Necessary(CompositeResponse.java:67)
at edu.cmu.cs.stage3.alice.core.response.CompositeRes ponse$RuntimeCompositeResponse.epilogue(CompositeR esponse.java:73)
at edu.cmu.cs.stage3.alice.core.response.CallToUserDe finedResponse$RuntimeCallToUserDefinedResponse.epi logue(CallToUserDefinedResponse.java:94)
at edu.cmu.cs.stage3.alice.core.behavior.AbstractCond itionalBehavior.internalSchedule(AbstractCondition alBehavior.java:112)
at edu.cmu.cs.stage3.alice.core.Behavior.schedule(Beh avior.java:226)
at edu.cmu.cs.stage3.alice.core.Sandbox.scheduleBehav iors(Sandbox.java:70)
at edu.cmu.cs.stage3.alice.core.World.scheduleBehavio rs(World.java:444)
at edu.cmu.cs.stage3.alice.core.World.schedule(World. java:486)
at edu.cmu.cs.stage3.alice.core.clock.DefaultClock.sc hedule(DefaultClock.java:99)
at edu.cmu.cs.stage3.alice.authoringtool.AuthoringToo l$7.run(AuthoringTool.java:702)
at edu.cmu.cs.stage3.alice.authoringtool.util.Default Scheduler.simulateOnce(DefaultScheduler.java:115)
at edu.cmu.cs.stage3.alice.authoringtool.util.Default Scheduler.run(DefaultScheduler.java:76)
at edu.cmu.cs.stage3.scheduler.AbstractScheduler.run( AbstractScheduler.java:45)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierar chy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.Dialog$1.run(Unknown Source)
at java.awt.Dialog$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.awt.Dialog.show(Unknown Source)
at java.awt.Component.show(Unknown Source)
at java.awt.Component.setVisible(Unknown Source)
at edu.cmu.cs.stage3.swing.DialogManager.showModalDia log(DialogManager.java:60)
at edu.cmu.cs.stage3.swing.DialogManager.showDialog(D ialogManager.java:128)
at edu.cmu.cs.stage3.alice.authoringtool.AuthoringToo l.play(AuthoringTool.java:5159)
at edu.cmu.cs.stage3.alice.authoringtool.Actions$15.a ctionPerformed(Actions.java:168)
at javax.swing.AbstractButton.fireActionPerformed(Unk nown Source)
at javax.swing.AbstractButton$Handler.actionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed (Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseRe leased(Unknown Source)
at java.awt.AWTEventMulticaster.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent( Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(U nknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unkno wn Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierar chy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Please help with this! I want to make a realistic walk motion without an annoying error.