Fix of ungroup bug

[Victor Stinner <victor stinner haypocalc com>]

Hi,

I wrote a patch to fix the "ungroup" bug (looks important since 3 people send 
bug report with CRITICAL level) in Dia. The bug was hard to understand
(memory free()'d), but easy to fix.

Please look at:
http://bugzilla.gnome.org/show_bug.cgi?id=334771
( duplicate: http://bugzilla.gnome.org/show_bug.cgi?id=338936 )

I can fix other bugs if it's possible to reproduce them under my computer
(Linux only).

Haypo
PS: I repost my email because I'm not sure that you received it and because I 
forgot the subject