Fix GiGraphics::_drawPolygon().
Fix GiGraphics::_drawPolygon().

xuebao555/vgcore,xuebao555/vgcore,aw691190716/vgcore,xuebao555/vgcore,aw691190716/vgcore,aw691190716/vgcore,xuebao555/vgcore,aw691190716/vgcore