safeguard not needed with a semaphore

callback_dispatcher.cc

@@ -29,8 +29,6 @@ namespace pEp {
             throw std::invalid_argument("messageToSend must be set");
 
         targets.push_back({messageToSend, notifyHandshake, on_startup, shutdown});
-
-        if (!Adapter::on_sync_thread())
         semaphore.go();
     }