Query tiflash_replica view with panic

[pcqz]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

mysql> create table t(a int);
Query OK, 0 rows affected (0.08 sec)

mysql> alter table t set tiflash replica 1;
Query OK, 0 rows affected (0.08 sec)

mysql> set tidb_replica_read='prefer-leader';
Query OK, 0 rows affected (0.00 sec)

mysql> select * from information_schema.tiflash_replica;
ERROR 1105 (HY000): runtime error: invalid memory address or nil pointer dereference

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

Execute the query successfully.

3. What did you see instead (Required)

[err="runtime error: invalid memory address or nil pointer dereference\ngithub.com/pingcap/tidb/store/copr.(*copIteratorWorker).handleTask.func1\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb/store/copr/coprocessor.go:1098\nruntime.gopanic\n\t/usr/local/go/src/runtime/panic.go:884\nruntime.panicmem\n\t/usr/local/go/src/runtime/panic.go:260\nruntime.sigpanic\n\t/usr/local/go/src/runtime/signal_unix.go:841\ngithub.com/tikv/client-go/v2/internal/locate.(*Store).recordSlowScoreStat\n\t/go/pkg/mod/github.com/tikv/client-go/[email protected]/internal/locate/region_cache.go:2949\ngithub.com/tikv/client-go/v2/internal/locate.(*RegionRequestSender).sendReqToRegion\n\t/go/pkg/mod/github.com/tikv/client-go/[email protected]/internal/locate/region_request.go:1621\ngithub.com/tikv/client-go/v2/internal/locate.(*RegionRequestSender).SendReqCtx\n\t/go/pkg/mod/github.com/tikv/client-go/[email protected]/internal/locate/region_request.go:1353\ngithub.com/tikv/client-go/v2/txnkv/txnsnapshot.(*ClientHelper).SendReqCtx\n\t/go/pkg/mod/github.com/tikv/client-go/[email protected]/txnkv/txnsnapshot/client_helper.go:146\ngithub.com/pingcap/tidb/store/copr.(*copIteratorWorker).handleTaskOnce\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb/store/copr/coprocessor.go:1197\ngithub.com/pingcap/tidb/store/copr.(*copIteratorWorker).handleTask\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb/store/copr/coprocessor.go:1108\ngithub.com/pingcap/tidb/store/copr.(*copIteratorWorker).run\n\t/home/jenkins/agent/workspace/build-common/go/src/github.com/pingcap/tidb/store/copr/coprocessor.go:801\nruntime.goexit\n\t/usr/local/go/src/runtime/asm_amd64.s:1598"]

4. What is your TiDB version? (Required)

v7.1.2

[pcqz]

/found gs

[cfzjywxk]

Duplicate with #47531, already fixed in client-go tikv/client-go#1017.