Using tpGlibClient branch of Empathy's git repository, if I set presence to offline the set back to available Empathy crash. This is because empathy uses weak_object to disconnect MembersChanged signal, but when the EmpathyTpGroup object is finalized the TpProxy is already invalidated so tp_proxy_signal_connection_disconnect() calls tp_proxy_borrow_interface_by_id() which returns NULL and the signal is not disconnected.
Fixed in Darcs, will be in 0.7.1.
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