moving startup code before register_sync_callbacks()

Adapter.hxx

@@ -17,13 +17,13 @@ namespace pEp {
 
         template< class T > void sync_thread(T *obj, function< void(T *) > _startup, function< void(T *) > _shutdown)
         {
+            if (obj && _startup)
+                _startup(obj);
+
             PEP_STATUS status = register_sync_callbacks(session(), nullptr,
                 _notifyHandshake, _retrieve_next_sync_event);
             throw_status(status);
 
-            if (obj && _startup)
-                _startup(obj);
-
             do_sync_protocol(session(), (void *)obj);
             unregister_sync_callbacks(session());