Windows: crash in QProcessPrivate::findExitCode

I already created QTBUG-33731 2 years ago. But this issue is closed after certain fixes... but that don't work fully.

The bug is easy to understand:

_q_processDied() is called twice

1) Once by the signal QWinEventNotifier::activated
This causes cleanup() to be called, and pid to be set to 0

Later:

2) QProcessPrivate::waitForFinished
_q_processDied is called after if (WaitForSingleObject...

since pid is 0, the crash occurs in QProcessPrivate::findExitCode

Q_ASSERT(pid) in triggered in debug mode, and in release mode, you crash.

I looked at 5.6 alpha code, and don't see anything to solve this.