XMLHttpRequest fails after open() if built with QApplication

I was working on this personal project: https://github.com/librehat/kesdict and found out that if I use QApplication instead of QGuiApplication in the main.cpp, the XMLHttpRequest will fail at stage 'OPEN'. The error handler also doesn't capture any failures when logging the event (it prints as undefined).

The same issue when I use qmlscene to launch the QML directly.

Note that I cannot reproduce this issue on my macbook (Brew installed Qt 5.14.1)