[SOLVED] Performance (Costs) - NullPointerException

SEVERE: Process failed: operator cannot be executed. Check the log messages...
java.lang.NullPointerException
        at com.rapidminer.example.Example.getNominalValue(Example.java:102)
        at com.rapidminer.operator.performance.cost.ClassificationCostCriterion.countExample(ClassificationCostCriterion.java:128)
        at com.rapidminer.operator.performance.cost.CostEvaluator.doWork(CostEvaluator.java:127)
        at com.rapidminer.operator.Operator.execute(Operator.java:834)
        at com.rapidminer.operator.execution.SimpleUnitExecutor.execute(SimpleUnitExecutor.java:51)
        at com.rapidminer.operator.ExecutionUnit.execute(ExecutionUnit.java:711)
        at com.rapidminer.operator.validation.ValidationChain.executeEvaluator(ValidationChain.java:223)
        at com.rapidminer.operator.validation.ValidationChain.evaluate(ValidationChain.java:324)
        at com.rapidminer.operator.validation.SplitValidationOperator.estimatePerformance(SplitValidationOperator.java:160)
        at com.rapidminer.operator.validation.ValidationChain.doWork(ValidationChain.java:273)
        at com.rapidminer.operator.Operator.execute(Operator.java:834)
        at com.rapidminer.operator.execution.SimpleUnitExecutor.execute(SimpleUnitExecutor.java:51)
        at com.rapidminer.operator.ExecutionUnit.execute(ExecutionUnit.java:711)
        at com.rapidminer.operator.OperatorChain.doWork(OperatorChain.java:379)
        at com.rapidminer.operator.Operator.execute(Operator.java:834)
        at com.rapidminer.Process.run(Process.java:925)
        at com.rapidminer.Process.run(Process.java:848)
        at com.rapidminer.Process.run(Process.java:807)
        at com.rapidminer.Process.run(Process.java:802)
        at com.rapidminer.Process.run(Process.java:792)
        at com.rapidminer.gui.ProcessThread.run(ProcessThread.java:63)

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<process version="5.2.008">
  <context>
    <input>
      <location>//Samples/data/Iris</location>
    </input>
    <output/>
    <macros/>
  </context>
  <operator activated="true" class="process" compatibility="5.2.008" expanded="true" name="Process">
    <process expanded="true" height="152" width="145">
      <operator activated="true" class="split_validation" compatibility="5.2.008" expanded="true" height="112" name="Validation" width="90" x="45" y="30">
        <process expanded="true" height="445" width="258">
          <operator activated="true" class="auto_mlp" compatibility="5.2.008" expanded="true" height="76" name="AutoMLP" width="90" x="45" y="30"/>
          <connect from_port="training" to_op="AutoMLP" to_port="training set"/>
          <connect from_op="AutoMLP" from_port="model" to_port="model"/>
          <portSpacing port="source_training" spacing="0"/>
          <portSpacing port="sink_model" spacing="0"/>
          <portSpacing port="sink_through 1" spacing="0"/>
        </process>
        <process expanded="true" height="445" width="258">
          <operator activated="true" class="performance_costs" compatibility="5.2.008" expanded="true" height="76" name="Performance" width="90" x="45" y="30">
            <parameter key="cost_matrix" value="[0.0 1.0 10.0;3.0 0.0 0.3;1.0 1.0 0.0]"/>
            <enumeration key="class_order_definition">
              <parameter key="class_name" value="Iris-setosa"/>
              <parameter key="class_name" value="Iris-virginica"/>
              <parameter key="class_name" value="Iris-versicolor"/>
            </enumeration>
          </operator>
          <connect from_port="test set" to_op="Performance" to_port="example set"/>
          <connect from_op="Performance" from_port="performance" to_port="averagable 1"/>
          <portSpacing port="source_model" spacing="0"/>
          <portSpacing port="source_test set" spacing="0"/>
          <portSpacing port="source_through 1" spacing="0"/>
          <portSpacing port="sink_averagable 1" spacing="0"/>
          <portSpacing port="sink_averagable 2" spacing="0"/>
        </process>
      </operator>
      <connect from_port="input 1" to_op="Validation" to_port="training"/>
      <connect from_op="Validation" from_port="model" to_port="result 2"/>
      <connect from_op="Validation" from_port="training" to_port="result 1"/>
      <connect from_op="Validation" from_port="averagable 1" to_port="result 3"/>
      <portSpacing port="source_input 1" spacing="0"/>
      <portSpacing port="source_input 2" spacing="0"/>
      <portSpacing port="sink_result 1" spacing="0"/>
      <portSpacing port="sink_result 2" spacing="0"/>
      <portSpacing port="sink_result 3" spacing="0"/>
      <portSpacing port="sink_result 4" spacing="0"/>
    </process>
  </operator>
</process>