QCFSocketNotifier: initialize member variable to avoid crash

The function pointer "maybeCancelWaitForMoreEvents" was never
initialized to any value. This caused qt_mac_socket_callback
to call that "function" when it had a non-zero value, which caused
a crash under some circumstances.

Change-Id: I1d31be7b5b7c103fdc0204ffa6e9a5ecbb28d062
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>

src/platformsupport/cfsocketnotifier/qcfsocketnotifier.cpp

@@ -101,6 +101,7 @@ void qt_mac_remove_socket_from_runloop(const CFSocketRef socket, CFRunLoopSource
 
 QCFSocketNotifier::QCFSocketNotifier()
 :eventDispatcher(0)
+, maybeCancelWaitForMoreEvents(0)
 {
 
 }