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".
just a guess: could it be that you have less then 10 texts? Just set the cross validation into "leave-one-out" mode and check again. The leave-one-out mode should also work if you have only few examples.
I tried to insert 20 texts, but it still doesn't work. So I've activated the rapidminer.general.debugmode in my preferences and the error that I get is:
And the window allows me to send a bug report.
If i set the cross validation into "leave-one-out" mode I get the same problem, but the Message changes in "Message: 18".
A curious thing is that if I use another learner such as LibSVMLearner it seems to work.
could you please make a screenshot directly after the StringTextInput? So we could have a look at the structure of the data set (meta data and data view if they are not too sensible). Maybe this gives us an idea where to search for a problem.