wallpapers/potd: manually call `destroy()` to free scarce data
This is a workaround for https://bugreports.qt.io/browse/QTBUG-73388 because passing QImage in QML can cause severe memory leaks.
Edited by Fushan Wen
This is a workaround for https://bugreports.qt.io/browse/QTBUG-73388 because passing QImage in QML can cause severe memory leaks.