unstable test TestLoadDataAutoRandomWithSpecialTerm

[hawkingrei]

Bug Report

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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)