defensive handle None

Signed-off-by: tison <wander4096@gmail.com>

src/promql/src/extension_plan/series_divide.rs

@@ -262,14 +262,20 @@ impl Stream for SeriesDivideStream {
                         Some(Ok(next_batch)) => next_batch,
                         None => {
                             self.num_series += 1;
-                            let batch = self.buffer.take().expect("must be some batch");
-                            return Poll::Ready(Some(Ok(batch)));
+                            return Poll::Ready(self.buffer.take().map(Ok));
                         }
                         error => return Poll::Ready(error),
                     };
-                    let batch = self.buffer.take().expect("must be some batch");
-                    let new_batch = compute::concat_batches(&batch.schema(), &[batch, next_batch])?;
-                    self.buffer = Some(new_batch);
+                    match self.buffer.take() {
+                        None => {
+                            self.buffer = Some(next_batch);
+                        }
+                        Some(batch) => {
+                            let new_batch =
+                                compute::concat_batches(&batch.schema(), &[batch, next_batch])?;
+                            self.buffer = Some(new_batch);
+                        }
+                    }
                     continue;
                 } else {
                     let result_batch = batch.slice(0, same_length);