Windows: QProcess::waitForFinished / QProcessPrivate::drainOutputPipes crash

What happen is this:
while this line is executed (in qprocess_win.cpp / QProcessPrivate::drainOutputPipes)

readyReadEmitted |= stdoutReader->waitForReadyRead(0);

much stuff is being executed (espesically QProcessPrivate::destroyChannel is called) and stdoutReader becomes 0,
hence the line following causes a crash (in QProcessPrivate::drainOutputPipes):

readOperationActive = stdoutReader->isReadOperationActive();

I fix the problem by simply testing
if (stdoutReader) again
and further if (stderrReader)

Note: my code was not revealling this problem with Qt 4.8.5