QTI 2.1 Problem when no answers selected

With the question types:

• Drag & Drop
• Match
• Hotspot

it is possible so select no correct answer and use it in a test (see picture match.jpg as example).

If the question is now answered correct (by not selecting any answer possibility) the Output Data delievers "FEEDBACKBASIC:  empty" and no point (match1.jpg) although it would be correct.

Therefore it should be mandatory for these question types to have at least 1 right answer, like it is for multiple choice.