QPainter warnings when using Metacity Window Manager and resizing a window down to it's minimum size

QPainter may in some cases print out warnings when using the Metacity window manager and resizing a window down to it's minimum size, the warnings will read as follows

QPainter::begin: Paint device returned engine == 0, type: 3
QPainter::setWorldTransform: Painter not active
QPainter::end: Painter not active, aborted
QPixmap::fromImage: Cannot convert a null image
QPainter::begin: Paint device returned engine == 0, type: 3
QPainter::setWorldTransform: Painter not active
QPainter::end: Painter not active, aborted
QPixmap::fromImage: Cannot convert a null image