test: eliminate last partial in empty table test by avoiding closures

Author: XuQianJin-Stars

rust/lance-namespace-impls/src/dir.rs

@@ -5772,8 +5772,8 @@ mod tests {
 
             let cursor = Cursor::new(bytes.to_vec());
             let reader = StreamReader::try_new(cursor, None).unwrap();
-            let total_rows: usize = reader.flatten().map(|b| b.num_rows()).sum();
-            assert_eq!(total_rows, 0);
+            let batches: Vec<_> = reader.collect::<std::result::Result<Vec<_>, _>>().unwrap();
+            assert!(batches.is_empty(), "empty table should yield no batches");
         }
 
         #[tokio::test]