Fix a strange warning seen on the log from the CI on Windows in
https://github.com/owncloud/client/pull/6621
The test shows, at the beginning
QObject::connect: No such signal DesktopServiceHook::destroyed(QObject*)
And crashes at the and.
My guess is that when QDesktopServices::setUrlHandler is called, the
QMetaObject is not yet initialized
But this is probably not the reason of the crash