Cannot use ingest way to add index for empty table

[tangenta]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Create a new cluster.

create table t (a int);
alter table t add index idx(a);
admin show ddl jobs 1;

2. What did you expect to see? (Required)

+--------+-------------+------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+
| JOB_ID | DB_NAME     | TABLE_NAME | JOB_TYPE               | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME         | START_TIME          | END_TIME            | STATE  |
+--------+-------------+------------+---------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+
|     88 | addindexlit | t          | add index /* ingest */ | public       |        84 |       86 |         0 | 2022-12-05 23:43:20 | 2022-12-05 23:43:20 | 2022-12-05 23:43:21 | synced |
+--------+-------------+------------+------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+

3. What did you see instead (Required)

+--------+-------------+------------+---------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+
| JOB_ID | DB_NAME     | TABLE_NAME | JOB_TYPE                  | SCHEMA_STATE | SCHEMA_ID | TABLE_ID | ROW_COUNT | CREATE_TIME         | START_TIME          | END_TIME            | STATE  |
+--------+-------------+------------+---------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+
|     88 | addindexlit | t          | add index /* txn-merge */ | public       |        84 |       86 |         0 | 2022-12-05 23:43:20 | 2022-12-05 23:43:20 | 2022-12-05 23:43:21 | synced |
+--------+-------------+------------+---------------------------+--------------+-----------+----------+-----------+---------------------+---------------------+---------------------+--------+

4. What is your TiDB version? (Required)

71863b4

[tangenta]

Tables with empty partitions will also encounter this problem. Change the severity to major.