Call QtWebView::initialize() write Warning: QtWebEngine::initialize() called with QCoreApplication object already created and should be call before. This is depreciated and may fail in the future.

QtWebEngine::initialize();

void initialize()
    {
        QCoreApplication *app = QCoreApplication::instance();
        if (app) {
            qWarning("QtWebEngine::initialize() called with QCoreApplication object already created and should be call before. "\
                 "This is depreciated and may fail in the future.");
            QtWebEngineCore::initialize();
            return;
        }
        // call initialize the same way as widgets do
        qAddPreRoutine(QtWebEngineCore::initialize);
    }