QSGDefaultRectangleNode always returns invalid color

When creating a QSGDefaultRectangleNode using QQuickWindow::createRectangleNode(), calling color() on the resulting node always returns QColor(Invalid), even after setting a valid color using setColor().

Internally, QSGDefaultRectangleNode uses a member variable m_color for the color() getter. However, this member is never updated in setColor(), which causes color() to return the default-initialized (invalid) color value, regardless of what was actually set.