Little black box covers part of the UI when running qBT under KDE

[ceodoe]

Please provide the following information

qBittorrent version and Operating System

4.2.5, Kubuntu (KDE desktop environment)

If on linux, libtorrent-rasterbar and Qt version

What is the problem

qBT will after running for a while produce a weird, black box in the intersection between the sidebar and the torrent list. If the program is restarted, the box disappears, but will eventually reappear after running for a while:

What is the expected behavior

No black box

Steps to reproduce

Start qBT under KDE, use program as normal, after running for some time the black box crops up (but I don't know if there's anything specific that causes it)

Extra info(if any)

Happens with both Breeze themes, both light and dark.

[njaard]

This problem exists in KMail and in both cases it seems to be be over a QSplitter

[njaard]

This has been fixed upstream: https://bugs.kde.org/show_bug.cgi?id=431921

👏