jdts 2.1_b06 + javatest 4.1.2_b04
Should be reproducible with a sample TestSuite

1. Create Interview that has a PropertiesQuestion.
2. Add one property to this question: new Properties() with one entry A= (empty string), then setValue(properties).
3. Set a ValueConstaraints for property A: setConstraints("A", new ValueConstraints(true /*readonly*/, false /*visible*/))
4. Try to edit such interview.
5. Configuration editor will show NO UIControl for such PropertiesQuestion - because it has no visible rows. But it will block the further actions saying that the Question has invalid value.