synchronization on finalization finally solved.

rktwebview.cpp

@@ -248,10 +248,9 @@ void rkt_evt_guard(void)
                 handler->evt_queue->enqueue(wv, data);
                 handler->evt_cb_mutex.lock();
                 if (handler->evt_cb != nullptr) {       // evt_cb could be cleared to null
-                    INFO2("Calling evt_cb with %d, %s\n", wv, data.c_str());
-
+                    //INFO2("Calling evt_cb with %d, %s\n", wv, data.c_str());
                     handler->evt_cb(1);
-                    INFO0("done\n");
+                    //INFO0("done\n");
                 } else {
                     INFO0("evt_cb = null\n");
                 }