fix qt5 build

Zhao Yuhang

2023-12-14 ca6ba7d7aa547b4e0c8d86fb9e00f25374a181db

 src/widgets/widgetwindowagent.cpp

@@ -57,6 +57,9 @@
        if (!d->context->setTitleBar(w)) {
            return;
        }
#ifdef Q_OS_MACOS
        d->setupMacOSTitleBar(w);
#endif
        Q_EMIT titleBarWidgetChanged(w);
    }