#7 error in Converter tutorial

[Russell Seidel]

null
Error
This NullPointerException error came up while analyzing ConverterRangeModel.java. All this class does is create the converter model for the converter GUI.

Fri Nov 18 21:05:36 EST 2011
CriticAL framework encountered a problem while analyzing:
[Class: test.ConverterRangeModel]
[Method: <test.converterrangemodel: void="" firestatechanged()="">]</test.converterrangemodel:>
[Line Number: 177]

java.lang.NullPointerException
at edu.clarkson.serl.critic.interpreter.internal.StackFrame.put(StackFrame.java:283)
at edu.clarkson.serl.critic.interpreter.model.StmtAssign.executeStmt(StmtAssign.java:90)
at edu.clarkson.serl.critic.interpreter.model.StmtAbstract.execute(StmtAbstract.java:111)
at edu.clarkson.serl.critic.interpreter.Interpreter.processContext(Interpreter.java:373)
at edu.clarkson.serl.critic.interpreter.Interpreter.execute(Interpreter.java:284)
at edu.clarkson.serl.critic.jobs.internal.CriticMainJob.run(CriticMainJob.java:86)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)