Comment 11 for bug 410432

nope, no NULL, BUT (running from konsole helps from time to time)
libxcb: WARNING! Program tries to lock an already locked connection,
        which indicates a programming error.
        There will be no further warnings about this issue.
xdndHandleBadwindow returned true
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
libxcb: WARNING! Program tries to unlock a connection without having acquired
        a lock first, which indicates a programming error.
        There will be no further warnings about this issue.

^^^ means: good chances
manager->object->deleteLater(); has been called... (manager being QDragManager::self())

IN ADDITION:
it happens with other (all?!) fullscreen FX, too (tried with present windows)

the problem seems to be that Qt gets confused on the window below the drag, defers a manager deletion but still manages to enter the eventfilter and then runs into the dying object?! (i'm a little confused, but at least the crash can not be reproduced in a deterministic way. e.g. testing with Qt's dnd example "draggableicons", it segfaults in about 1 of maaany cases :-(