applets/showActivityManager: Only show activityManager when drag contains windows
It doesn't make sense to show it on something that can't be dropped into it. This fixes the crash in the mentioned bug but there is a more general issue that applets can interfere with the edit mode widget dragging. BUG:492624 FIXED-IN:6.1.5
(cherry picked from commit d4b87ac6)
Co-authored-by: David Redondo kde@david-redondo.de