Don't panic on empty insert

Fixes #137

src/insert.rs

@@ -84,8 +84,8 @@ impl InsertState {
     }
 
     fn terminated(&mut self) {
-        debug_assert!(matches!(self, InsertState::Active { .. }));
         replace_with_or_abort(self, |_self| match _self {
+            InsertState::NotStarted { .. } => InsertState::Completed,
             InsertState::Active { handle, .. } => InsertState::Terminated { handle },
             _ => unreachable!(),
         });

tests/it/insert.rs

@@ -99,3 +99,28 @@ async fn overrides_client_options() {
     let rows = fetch_simple_rows(&client, table_name).await;
     assert_eq!(rows, vec!(row))
 }
+
+#[tokio::test]
+async fn empty_insert() {
+    // https://github.com/ClickHouse/clickhouse-rs/issues/137
+
+    let table_name = "insert_empty";
+    let query_id = uuid::Uuid::new_v4().to_string();
+    let (setting_name, setting_value, override_value) = ("async_insert", "0", "1");
+
+    let client = prepare_database!().with_option(setting_name, setting_value);
+    create_simple_table(&client, table_name).await;
+
+    let insert = client
+        .insert::<SimpleRow>(table_name)
+        .unwrap()
+        .with_option(setting_name, override_value)
+        .with_option("query_id", &query_id);
+
+    insert.end().await.unwrap();
+
+    flush_query_log(&client).await;
+
+    let rows = fetch_simple_rows(&client, table_name).await;
+    assert!(rows.is_empty())
+}