Configuring CSV input, unable to load sample CSV file

At some point during the switch from the Smooks-DMB branch back to trunk to implement the Direct Source to Target mapping, we managed to disable the ability to select a CSV file for the sample input of the Input Task.

To reproduce:

1. Create a new Smooks file.
2. Set the input task "input type" to CSV
3. Try to click the Add button in the Input Data section.
4. Get nothing, see NPE in the .log file.