alice-teacher Very strange runtime errors

[Roger Wistar]

One of my students is having very strange runtime errors in Alice 2.2b (8/5/2011) on a Mac when trying to run his Tic Tac Toe program. (N.B.: we were forced to downgrade to the 8/5 version because of the bug in passing parameters between methods.) In his program, we see the following errors:

1) As soon as a player clicks one of the squares, triggering a call to the World.whoWon() function, the program crashes with an "Error during simulation" message:

Error during simulation.
Alice version: 2.2  08/05/2011
Throwable that caused the error:
java.lang.NullPointerException
at edu.cmu.cs.stage3.alice.core.question.userdefined.PropertyAssignment.execute(PropertyAssignment.java:73)
(rest of error output cut for brevity)

2) When we try to open the whoWon() function, we get an error message "An error occurred while creating the graphics component for this object":

An error occurred while creating the graphics component for this object.
Alice version: 2.2  08/05/2011
Throwable that caused the error:
java.lang.NullPointerException
at edu.cmu.cs.stage3.alice.authoringtool.AuthoringToolResources.getReprForValue(AuthoringToolResources.java:704)
(rest of error output cut for brevity)


I can't see anything obvious that he is doing wrong and I am worried that somehow his program has become corrupted. It would be a shame if he had to recreated it all from scratch. How can I solve this problem? I've attached his program here. Please help!


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