The ExampleSet has no examples

Hi,
I get a similar error in my process. Inside the XVal (Cross Validation), till the Naive Bayes learner everything works great, but in the second operator (the OperatorChain) i can't get my ExampleSet and the ModelApplier obviously returns an empty result, which gives me an error in the ClassificationPerformance operator.

The error returned is "The ExampleSet has no examples".

Here a screenshot of a breakpoint after the ModelApplier: http://i35.tinypic.com/wgt3bk.png
Here a screenshot of the Cross Validator operator: http://i33.tinypic.com/2jcvhww.png
Here a screenshot of the NaiveBayes learner: http://i37.tinypic.com/5b4o4j.png

Here is che XML (note, I've updated the Text-Plugin up to the 4.1 version, with the correction of the DatabaseExampleSource bug)


<operator name="Root" class="Process" expanded="yes">
<operator name="Database Source" class="DatabaseExampleSource">
<parameter key="database_url" value="jdbc:mysql://localhost:3306/tesi"/>
<parameter key="id_attribute" value="indice"/>
<parameter key="label_attribute" value="label"/>
<parameter key="password" value="OB3A2Q0OV20="/>
<parameter key="query" value="/*&#10;&#09;Interrogazione Database&#10;*/&#10;&#10;&#10;&#10;SELECT indice, CONCAT(empty1, &#39; &#39;, indirizzo, &#39; &#39;, empty2) AS text_source, class AS label&#10;FROM `outrec2` &#10;WHERE indirizzo IS NOT NULL AND NOT (indirizzo=&#39;&#39;)&#10;LIMIT 0 , 3"/>
<parameter key="username" value="root"/>
</operator>
<operator name="StringTextInput" class="StringTextInput" expanded="no">
<parameter key="filter_nominal_attributes" value="true"/>
<list key="namespaces">
</list>
<operator name="StringTokenizer" class="StringTokenizer">
</operator>
<operator name="StopwordFilterFile" class="StopwordFilterFile">
<parameter key="file" value="D:\Tesi\stopwords.txt"/>
</operator>
<operator name="TokenLengthFilter" class="TokenLengthFilter" activated="no">
<parameter key="min_chars" value="3"/>
</operator>
<operator name="PorterStemmer" class="PorterStemmer" activated="no">
</operator>
</operator>
<operator name="XValidation" class="XValidation" expanded="yes">
<parameter key="sampling_type" value="shuffled sampling"/>
<operator name="NaiveBayes" class="NaiveBayes">
<parameter key="keep_example_set" value="true"/>
<parameter key="use_kernel" value="true"/>
</operator>
<operator name="Analyzer" class="OperatorChain" expanded="yes">
<operator name="ModelApplier" class="ModelApplier">
<list key="application_parameters">
</list>
</operator>
<operator name="ClassificationPerformance" class="ClassificationPerformance">
<list key="class_weights">
</list>
<parameter key="classification_error" value="true"/>
<parameter key="main_criterion" value="classification_error"/>
</operator>
</operator>
</operator>
</operator>




Thank you