Aborting a DnD from drag-begin using gtk_drag_finish raises critical warning

[Chris Seaton <chris chrisseaton com>]

Hello,

I have a tree view with list store that I've set up as a drag source. 
I'm not using the tree view DnD wrappers as in my application I want to 
drop into the items in another tree view, and with the wrappers it gives 
feedback as if it were going to insert between the items, and not drop 
into them.

When the user drags and there is nothing selected I want to abort the 
drag. I'm testing to see if anything is selected in the drag-begin 
handler, but when I use gtk_drag_finish I'm warned

(cspassword:9503): Gtk-CRITICAL **: file gtkdnd.c: line 717 
(gtk_drag_finish): assertion `!context->is_source' failed

Stack trace (not terribly interesting)

#0  0x00485c32 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1  0x00b8998f in raise () from /lib/tls/libc.so.6
#2  0x00b8b302 in abort () from /lib/tls/libc.so.6
#3  0x0062af38 in g_logv () from /usr/lib/libglib-2.0.so.0
#4  0x0062af74 in g_log () from /usr/lib/libglib-2.0.so.0
#5  0x00820d6d in gtk_drag_finish () from /usr/lib/libgtk-x11-2.0.so.0
#6  0x08050076 in Accounts_OnDragBegin (Widget=0x9847f18, Context=0x98d2710,
    User=0x0) at accounts.c:152
#7  0x003a8d4e in g_cclosure_marshal_VOID__OBJECT ()
   from /usr/lib/libgobject-2.0.so.0
#8  0x00395cb0 in g_closure_invoke () from /usr/lib/libgobject-2.0.so.0
#9  0x003a7bbf in g_signal_emit_by_name () from /usr/lib/libgobject-2.0.so.0
#10 0x003a6c36 in g_signal_emit_valist () from /usr/lib/libgobject-2.0.so.0

What am I doing wrong?

Thanks.

Chris Seaton