I have applications in Icon-only Task Manager that have "Show A Launcher When Not Running" enabled. When I quit such application, it's icon disappears in Icon-only Task Manager for < 0.5s. The place where the icon was becomes blank. After a very short duration, the icon comes back and works normally.

It seems that when a task changes state from running application to a launcher, the Task QML object for it gets recreated. Task QML component uses PlasmaCore.ItemItem for showing the icon. PlasmaCore.IconItem loads the icon asynchronously, causing the icon to be invisible for a while.

If I replace PlasmaCore.IconItem with a QIconItem in plasma-desktop/applets/taskmanager/package/contents/ui/Task.qml, the issues becomes fixed. This is not a proper fix since QIconItem lacks active hover effect.

Reproducible: Always

Steps to Reproduce:
1. Use Icon-only Task Manager as task manager
2. Open an application
3. Enable "Show A Launcher When Not Running"  for the application in Icon-only Task Manager
4. Quit the application

Actual Results:  
The application's icon disappears in Icon-only Task Manager for < 0.5s.

Expected Results:  
The application's icon stays same.