Unprotected access to the devMode-member of QWin32PrintEngine may cause crash

Under some conditions some printer driver returns a null-pointer when retrieving the devMode-pointer. In these cases the app crashes while printing in QWin32PrintEngine::begin(...) when num_copies-value should be set into the devMode.

Additional feed back on this issue:
The problem of nul-DEVMODE's is that Qt retrieve the DEVMODE only from the PRINTER_INFO_2 struct which is not filled correctly especially by some none-microsoft printer drivers. It is suggested to retrieve a valid devmode in an alternative way as decribed in http://www.codeguru.com/forum/showthread.php?t=93941 if
PRINTER_INFO_2's pDevMode points to null.