Parsing attributes failed and causes panic

[djshow832]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

mysql-connector-java-5.1.34.jar connects to TiProxy

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

No error.

3. What did you see instead (Required)

2023-05-19 12:25:29 [2023/05/19 02:25:29.199 +00:00] [INFO] [main.proxy] [proxy/proxy.go:170] [new connection] [connID=177] [client_addr=172.30.73.242:16110]2023-05-19 12:25:29 [2023/05/19 02:25:29.199 +00:00] [INFO] [main.proxy] [proxy/proxy.go:170] [new connection] [connID=177] [client_addr=172.30.73.242:16110]2023-05-19 12:25:29 [2023/05/19 02:25:29.282 +00:00] [INFO] [main.proxy] [proxy/proxy.go:181] [connection closed] [connID=177] [client_addr=172.30.73.242:16110]2023-05-19 12:25:29 panic: runtime error: invalid memory address or nil pointer dereference2023-05-19 12:25:29 [signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x126b3e1]2023-05-19 12:25:29 2023-05-19 12:25:29 goroutine 2302510 [running]:2023-05-19 12:25:29 github.com/pingcap/TiProxy/pkg/proxy/backend.(*Authenticator).handshakeFirstTime(0xc000bbdf90, 0xd?, {0x18681d0, 0xc00043e340}, 0xc0003eebe0, {0x185e720, 0xc000127328}, 0xc0011cda30, 0xc0004b0a80, 0x0)2023-05-19 12:25:29 /proxy/pkg/proxy/backend/authenticator.go:161 +0xa412023-05-19 12:25:29 github.com/pingcap/TiProxy/pkg/proxy/backend.(*BackendConnManager).Connect(0xc00043e340, {0x185d020, 0xc000415a40}, 0xc0003eebe0, 0x7fcadb6d30c0?, 0x0)2023-05-19 12:25:29 /proxy/pkg/proxy/backend/backend_conn_mgr.go:174 +0x1a72023-05-19 12:25:29 github.com/pingcap/TiProxy/pkg/proxy/client.(*ClientConnection).Run(0xc000e7dd10, {0x185d020, 0xc000415a40})2023-05-19 12:25:29 /proxy/pkg/proxy/client/client_conn.go:58 +0x592023-05-19 12:25:29 github.com/pingcap/TiProxy/pkg/proxy.(*SQLServer).onConn(0xc0005c20f0, {0x185d020, 0xc000415a40}, {0x186aa08, 0xc0004da0d0})2023-05-19 12:25:29 /proxy/pkg/proxy/proxy.go:190 +0xb752023-05-19 12:25:29 github.com/pingcap/TiProxy/pkg/proxy.(*SQLServer).Run.func2.1()2023-05-19 12:25:29 /proxy/pkg/proxy/proxy.go:132 +0x2d2023-05-19 12:25:29 github.com/pingcap/TiProxy/lib/util/waitgroup.(*WaitGroup).Run.func1()2023-05-19 12:25:29 /proxy/lib/util/waitgroup/waitgroup.go:33 +0x5a2023-05-19 12:25:29 created by github.com/pingcap/TiProxy/lib/util/waitgroup.(*WaitGroup).Run2023-05-19 12:25:29 /proxy/lib/util/waitgroup/waitgroup.go:31 +0x85

4. What is your version? (Required)

master