QImage::paintEngine() crashes when called on copy

Hello,

when creating a shallow copy of a QImage and calling paintEngine the internal QPaintEngine is not created properly.

#include <QImage>

int main()
{
    const QImage srcImage{"path/to/image"};
    assert(!srcImage.isNull());
    auto destImage = srcImage;
    assert(destImage.paintEngine() != nullptr);
    return EXIT_SUCCESS;
}

This application crashes at the assert because the paintengine is not created properly.
Calling QImage::copy to create a deep copy is a valid work around. Calling destImage.paintEngine one time before using leads also to creation of the PaintEngine in the right object.

Maybe the QImage class should be searched for missing detach() calls in all its non-const member functions.