QmlDesigner: Crash fix

This is likely to fix a crash we could only reproduce
with the Qt Design Studio release on one machine.

Task-number: QDS-270
Change-Id: Idc33ba145169613b866903fa5e259f8cd6ec4ee8
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

share/qtcreator/qml/qmlpuppet/container/imagecontainer.cpp

@@ -196,6 +196,9 @@ static void readSharedMemory(qint32 key, ImageContainer &container)
 
         QImage image = QImage(imageWidth, imageHeight, QImage::Format(imageFormat));
 
+        if (image.isNull())
+            qDebug() << Q_FUNC_INFO << "Not able to create image:" << imageWidth << imageHeight << imageFormat;
+        else
             std::memcpy(image.bits(), reinterpret_cast<const qint32*>(sharedMemory.constData()) + 5, byteCount);
 
         container.setImage(image);