Possible null pointer dereference in qpixmap.cpp

Issue

See https://code.qt.io/cgit/qt/qtbase.git/tree/src/gui/image/qpixmap.cpp#n78

qt_pixmap_thread_test() only checks for the presence of QCoreApplication, not QGuiApplication. As a result, it is possible for the function to dereference the nullptr returned by QGuiApplicationPrivate::platformIntegration() if the function is triggered without a QGuiApplication present.

Suggestion

Check for a QGuiApplication instead of just a QCoreApplication.

This way, even if a user (illegally) creates a QPixmap without a QGuiApplication, they will get a qFatal() assertion with a proper explanation, instead of a segfault without explanation.