check for init before render shutdown
check for init before render shutdown

we could shut down render without having inited it, check

thanks andrea

mcanthony/libvips,wishabi/libvips,wishabi/libvips,lovell/libvips,leiyangyou/libvips,mcanthony/libvips,lovell/libvips,leiyangyou/libvips,jcupitt/libvips,mcanthony/libvips,leiyangyou/libvips,jcupitt/libvips,wishabi/libvips,mcanthony/libvips,lovell/libvips,lovell/libvips,leiyangyou/libvips,jcupitt/libvips,wishabi/libvips,jcupitt/libvips