br: the br panic on tikv client-go when do backup

[joccau]

Bug Report

• BR version
  [release-version=v5.4.0] [git-hash=55f3b24c1c9f506bd652ef1d162283541e428872] [git-branch=heads/refs/tags/v5.4.0] [go-version=go1.16.4] [utc-build-time="2022-01-25 08:36:34"]

• Panic stack
  github.com/tikv/client-go/v2/internal/client.interceptedClient.SendRequest(0x40439a8, 0xc000c5b500, 0x4065210, 0xc0008fc580, 0xc000f99180, 0x39, 0xc00f6f1e00, 0x6fc23ac00, 0x203003, 0x203003, ...)
  --
  /nfs/cache/mod/github.com/tikv/client-go/v2@v2.0.0-rc.0.20211229051614-62d6b4a2e8f7/internal/client/client.go:410 +0x275
  /nfs/cache/mod/github.com/tikv/client-go/v2@v2.0.0-rc.0.20211229051614-62d6b4a2e8f7/internal/client/client_collapse.go:74 +0x12a
  /nfs/cache/mod/google.golang.org/grpc@v1.29.1/clientconn.go:514
  github.com/tikv/client-go/v2/internal/client.(*RPCClient).SendRequest(0xc000c5b500, 0x4065210, 0xc0008fc580, 0xc000f99180, 0x39, 0xc00f6f1e00, 0x6fc23ac00, 0x0, 0x0, 0x0)
  github.com/tikv/client-go/v2/internal/client.interceptedClient.SendRequest(0x40439a8, 0xc000c5b500, 0x4065210, 0xc0008fc580, 0xc000f99180, 0x39, 0xc00f6f1e00, 0x6fc23ac00, 0x203003, 0x203003, ...)
  I0524 03:58:28.807851 9 backup.go:100] panic: runtime error: invalid memory address or nil pointer dereference
   
  goroutine 13166 [running]:
  github.com/tikv/client-go/v2/internal/client.reqCollapse.SendRequest(0x4045a00, 0xc000adc030, 0x4065210, 0xc0008fc580, 0xc000f99180, 0x39, 0xc00f6f1e00, 0x6fc23ac00, 0x39e0f40, 0x1, ...)
  /nfs/cache/mod/github.com/tikv/client-go/v2@v2.0.0-rc.0.20211229051614-62d6b4a2e8f7/tikv/kv.go:538 +0x145
  I0524 03:58:28.807762 9 backup.go:93]
  [signal SIGSEGV: segmentation violation code=0x1 addr=0x228 pc=0x1d32b75]
  google.golang.org/grpc.(*ClientConn).GetState(...)
  github.com/tikv/client-go/v2/tikv.(*KVStore).updateSafeTS.func1(0x40439d0, 0xc000adc040, 0xc000a90640, 0x4065210, 0xc0008fc580, 0xc010991d20, 0x11, 0xc000f99180, 0x39)
  /nfs/cache/mod/github.com/tikv/client-go/v2@v2.0.0-rc.0.20211229051614-62d6b4a2e8f7/tikv/kv.go:540 +0x165
  created by github.com/tikv/client-go/v2/tikv.(*KVStore).updateSafeTS
  /nfs/cache/mod/github.com/tikv/client-go/v2@v2.0.0-rc.0.20211229051614-62d6b4a2e8f7/internal/client/client_interceptor.go:42 +0x1e9

• It is about https://jira.tidbcloud.com/browse/TCOC-451

[joccau]

• This issus is the same as the https://github.com/tikv/client-go/issues/505，fixed by Race between connArray.Get() and connArray.Close() tikv/client-go#464
• What we need is to update tikv/client-go

[joccau]

/assign

[joccau]

/close

[ti-chi-bot]

@joccau: Closing this issue.

In response to this:

/close

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