We check for a valid event dispatcher when waking up,
but there was no check after processing queued events,
and processEvents() would continue with a stale this
pointer if one of the queued events happened to delete
the application object.
Fix this by checking if this is still a valid pointer
after processing events.
Fixes: QTBUG-116330
Pick-to: 6.6 6.5
Change-Id: Ic4d91298986847e6095ce9daea51a4b974106c06
Reviewed-by: Piotr Wierciński <piotr.wiercinski@qt.io>
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
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