Fix segmentation fault in numbers_stream
`select * from system.numbers_mt(0)` will trigger a segmentation fault.  seems query-server should return `None` if an empty data-range is being pulled.
Change behavior of `NumbersStream::try_get_one_block` may also work.
@@ -100,6 +100,7 @@ impl Stream for NumbersStream {
Poll::Ready(match current {
None => None,
+ Some(current) if current.begin == current.end => None,
Some(current) => {
let v = (current.begin..current.end).collect::<Vec<u64>>();
let mut me = ManuallyDrop::new(v);
