minimal_asyncio.py example might lead to memory leak

running the asyncio miminal example which loads a qml file, the python process memory usage increase 10M per seconds, while there is nothing running in the backends.

here is the screen capture videos

https://drive.google.com/file/d/1guKyEj88joUOytk07RMke7-pPbwQOE0p/view?usp=sharing

it will collapse until running out of memories i guess

here is the example i running， 

the qml file it loads is just a simple window

import QtQuick 2.15
import QtQuick.Window 2.15

Window {
 id: window
 width: 400
 height: 500
 visible: true
}

change the AsyncHelper to qasync, the memory usage is stable, not growing any more