Summary:
It can happen that startAnimation is invoked multiple times for a
window. In case it was invoked a second time the previous animation was
not cancelled. This resulted in the set-animation to never end. When
closing a window, it would stay around as a translucent, non-interactive
window zombie.
This change ensures that existing animations get cancelled.
BUG: 342716
FIXED-IN: 5.8.3
Test Plan: Tested through autotest and manually.
Reviewers: #kwin, #plasma
Subscribers: plasma-devel, kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D3190
94c5704af7