[TYPO3-calendar] categories as comma separated list in events

[Heinz Schilling]

Hi to the list

For a XML interface I need the categories of a event. They are listed 
but not every category separeted from others.

I need: Kat A,Kat B
I have: Kat AKatB

Where must I wrap to insert the comma?

Thanks for helping.
Heinz