Multiple QNetworkRequest setRawHeader crash

If multiple QnetworkAccessManager are created in the application there is an error on the get call 

To reproduce this, use the same sample code than QTBUG-84685 and add those two lines in main.cpp

QNetworkAccessManager *qnam_2 = new QNetworkAccessManager();
 w.connect(qnam_2, &QNetworkAccessManager::finished, &w, &MainWindow::netReply);

It results in an exception on edge:

exception thrown: RuntimeError: memory access out of bounds,RuntimeError: memory access out of bounds

With only one QNAM, it works.