mysql tester crashes when transactions is not started and we commit

[Alkaagr81]

connect (con1,localhost,root,,test);

connection con1;
COMMIT;

so error message is

WARN[0000] Create new db&{0 {root:@tcp(127.0.0.1:4001)/test?strict=true&time_zone=%27Asia%2FShanghai%27 0x1059168} 0 {0 0} [0xc0001ee630] map[] 0 1 0xc000026240 false map[0xc0001ee630:map[0xc0001ee630:true]] map[] 0 0 0 0 <nil> 0 0 0 0 0x49cfa0} 
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x70 pc=0x4e6a06]

goroutine 7 [running]:
database/sql.(*Tx).Commit(0x0, 0x8edf28, 0x1)
	/usr/local/go/src/database/sql/sql.go:2151 +0x26
main.(*tester).commit(...)
	/home/morgo/go/pkg/mod/github.com/pingcap/mysql-tester@v0.0.0-20211026071309-3ee4da8b351d/src/main.go:673
main.(*tester).stmtExecute(0xc0001ee510, 0xc000024b57, 0x6, 0xc000024b57, 0x7, 0x2b, 0x2, 0x8fd648, 0xc00012e100, 0x1, ...)
	/home/morgo/go/pkg/mod/github.com/pingcap/mysql-tester@v0.0.0-20211026071309-3ee4da8b351d/src/main.go:566 +0xb6
main.(*tester).execute(0xc0001ee510, 0xc000024b57, 0x6, 0xc000024b57, 0x7, 0x2b, 0x2, 0x0, 0x0)
	/home/morgo/go/pkg/mod/github.com/pingcap/mysql-tester@v0.0.0-20211026071309-3ee4da8b351d/src/main.go:621 +0x13d
main.(*tester).Run(0xc0001ee510, 0x0, 0x0)
	/home/morgo/go/pkg/mod/github.com/pingcap/mysql-tester@v0.0.0-20211026071309-3ee4da8b351d/src/main.go:307 +0x666
main.testBatch.Run(0xc00000c1e0, 0x1, 0x1e)
	/home/morgo/go/pkg/mod/github.com/pingcap/mysql-tester@v0.0.0-20211026071309-3ee4da8b351d/src/main.go:928 +0xb3
created by main.executeTests
	/home/morgo/go/pkg/mod/github.com/pingcap/mysql-tester@v0.0.0-20211026071309-3ee4da8b351d/src/main.go:958 +0xc5
+ echo 'tidb-server(PID: 295933) stopped'
tidb-server(PID: 295933) stopped
+ kill -9 295933