unstable test TestLoadDataAutoRandomWithSpecialTerm

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

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

### 3. What did you see instead (Required)

```
dbtestkit.go:71:
Error Trace: testkit/dbtestkit.go:71
server/server_test.go:582
server/server_test.go:151
server/server_test.go:574
server/tidb_serial_test.go:88
Error: Received unexpected error:
Error 1105 (HY000): runtime error: index out of range [0] with length 0
Test: TestLoadDataAutoRandomWithSpecialTerm
Messages: sql:load data local infile "/tmp/load_data_txn_error_term.csv14369143" into table t1 fields terminated by ',' enclosed by '\'' lines terminated by '|' (c2, c3), args:[]
```

https://do.pingcap.net/jenkins/blue/organizations/jenkins/pingcap%2Ftidb%2Fghpr_unit_test/detail/ghpr_unit_test/19091/tests
### 4. What is your TiDB version? (Required)