Unexpected detach on setColorTable after QImage::QImage(const uchar *data, ...)

QImage offers two constructors that uses an existing read-only memory buffer given via const char*. If the image format is indexed, documentation requires the user to call "setColorCount() or setColorTable() before the image is used."

However, doing so forces detaching, which is against the purpose of using this constructor in the first place. It should be possible to at least initialize the color table without detaching.