JIPDA example didn't work

[ReyRizki]

Hello, currently I am doing a research about JIPDA and want to use the code. However, when I try to run JIPDA example, I found the following error:

Unrecognized function or variable 'xk'.

Error in ConstantDetectionProbabilityX/pdf (line 84)
            a = find(inpolygon(xk(1,:),xk(3,:),x,y));

Error in MultiTargetMeasurementSimulatorX/simulate (line 79)
            detectionProbability = this.Model.Detection.pdf();

Error in example (line 34)
DataList = meas_simulator.simulate(GroundTruthStateSequence);

I also have examined pdf function in ConstantDetectionProbabilityX and found that the error is caused by xk is only defined when there is more than 1 argument.

if(nargin>1)
    xk = varargin{1};
    Ns = size(xk,2);
end

Is there any fix to this problem?