protect nil response during vm.kill
protect nil response during vm.kill

Signed-off-by: Wang Xu <0e9dfdf30d71e7ded2bba4a3dc006039c4b00f3d@gmail.com>

wrouesnel/runv,gao-feng/runv,YaoZengzeng/runv,gao-feng/runv,laijs/runv,hyperhq/runv,jinfenw/runv,bergwolf/runv,bergwolf/runv,laijs/runv,laijs/runv,hyperhq/runv,jinfenw/runv,hyperhq/runv,feiskyer/runv,gnawux/runv,wrouesnel/runv,gnawux/runv,feiskyer/runv,jinfenw/runv,bergwolf/runv,gnawux/runv,YaoZengzeng/runv,gao-feng/runv