hobbitsvc.cgi returns Premature end of script headers

I have a mysterious constellation.

With one exception showing historical logs works fine.

Only one service for one host error an occurs (Premature end of script
headers).
The same service for another host works.

If I add --debug in the bb-histlog.sh, it works (and shows "Trying
header/footer file '/opt/hobbit/server/web/histlog_footer'").

So I played a litte with the hobbitsvc.c.
If I comment
	if (tstamp) xfree(tstamp);
in the function do_request, this one service for this one host works also!

My hobbit version is 4.2.0 with the all-in-one-Patch from Dec 15.

Michael