QWeakPointer is pretty much unusable for this purpose in Qt5. Its only
purpose is to represent a weak reference to a QSharedPointer.

BTW, QPointer has the big advantage of actually having implicit T* conversion
operator and operator->() so you don't have to use the data() method
everywhere. I converted some usages with a very conservative grep+sed:

git grep '\.data()->' | egrep -vi \
	'account|avatar|budd|group|chat|contact|file|identit|message|proxy|encryption_ng' \
	| cut -f1 -d: | sort -u | xargs sed -i 's/\.data()->/->/g'

Signed-off-by: Bartosz Brachaczek <b.brachaczek@gmail.com>