Created attachment 111085 [details]
start a new plasma session
press alt+space bar to open krunner, type "dolphin" and press enter to open it
press alt+space bar to open krunner, type "kate" and press enter to open it
hover the first entry in your task manager
My screenshot shows the result.
This bug is reproducible only when task manager has NO pinned icon.
*** This bug has been marked as a duplicate of bug 385947 ***