Well I have found this issue during analysis of existing cores, so I don't know the sequence how it can be reproduce. But the main thing is, in the presence mixin "tp_presence_mixin_simple_presence_register_with_contacts_mixin()" function we are registering the function "tp_presence_mixin_simple_presence_fill_contact_attributes()" and the implementation of this function calls mixin get contact statuses callback function "get_contact_statuses()" which return the GHashTable. The HashTable can be NULL as well in which case we need to check the error for reason. But in this function we have an assert if the hashtable is NULL. Which abort the process.