OutOfMemory + crash because of missing error checking in QWindowsPrintDevice

We found this callstack on a customer computer:

custom.dll!new_handler(unsigned int s) Zeile 773	C++ ** OUT OF MEMORY **
Qt5PrintSupport.dll!QPrintDevice::defaultPageSize() Zeile 137	C++
Qt5PrintSupport.dll!QWin32PrintEngine::QWin32PrintEngine(QPrinter::PrinterMode mode) Zeile 88	C++
Qt5PrintSupport.dll!QPrinterPrivate::initEngines(QPrinter::OutputFormat format, const QPrinterInfo & printer) Zeile 147	C++
Qt5PrintSupport.dll!QPrinter::QPrinter(QPrinter::PrinterMode mode) Zeile 684	C++

Unfortunately we were not able to reproduce it, because it seems to be system specitic.
But some investigation in defaultPageSize() leads to a missusage of DocumentProperties that will definitely end in an OutOfMemory exception.

The reason is simple:
DocumentProperties is used to fetch the current DEVMODE-structure in several functions of QWindowsPrintDevice.
But there is no error checking when DocumentProperties fails!
When DocumentProperties fails it returns a negative (signed!) value of type LONG, which ist stored in an unsigned variable of type DWORD, which now have a huge positive value.
Whithout error-checking ist is used to allocate memory of it's value, which will imho always fails.

Suggested fix would be like this

    // Allocate the required DEVMODE buffer
    LONG dmSize = DocumentProperties(NULL, m_hPrinter, (LPWSTR)m_id.utf16(), NULL, NULL, 0);
    if (dmSize > 0)
    {
       LPDEVMODE pDevMode = (LPDEVMODE)malloc(dmSize);

       // Get the default DevMode
       DWORD result = DocumentProperties(NULL, m_hPrinter, (LPWSTR)m_id.utf16(), pDevMode, NULL, DM_OUT_BUFFER);

       // Get the desired value

       // Clean-up
       free(pDevMode);
    }
    else if (dmSize < 0) {
       // some error handling needed
    }
    // no error when dmSize == 0