g_strconcat bugs in gnome-libs

[Lyndon Drake <lyndon stat auckland ac nz>]

Hi,

g_strconcat is used incorrectly in several files in gnome-libs/libgnome and
gnome-libs/libgnomeui.  The last argument in g_strconcat should be NULL, but sometimes
isn't, which can cause segmentation faults.  Fixing this stuff cleaned up a lot of
problems for me, which makes me wonder if va_arg returns NULL on Linux when it runs out
of arguments (if it does, it would explain why nobody has noticed the problems before).

In libgnome, the files are gnome-dentry.c, lines 121, 189, and 224, and gnome-util.c,
line 542.

I have lost my list of lignomeui files with the same problem.  I will post them later
this afternoon, or whoever fixes this on cvs could just do a grep for g_strconcat and
check the files themselves.

Lyndon