lease_id null causes connection hangups on some endpoints

[ludovicianul]

Describe the bug
The following endpoints are failing to respond when lease_id is null: /sys/leases/lookup, /sys/leases/renew and /sys/leases/revoke.

To Reproduce
Steps to reproduce the behavior:

curl  -X POST \
      -H "Accept: application/json" -H "Content-Type: application/json" -H "X-Vault-Token: $token" \
      -d '{"lease_id":null}' \
      http://localhost:8200/v1/sys/leases/lookup

curl  -X POST \
      -H "Accept: application/json" -H "Content-Type: application/json" -H "X-Vault-Token: $token" \
      -d '{"url_lease_id":"xA93aoKE2mSsv2h","sync":true,"lease_id":null}' \
      http://localhost:8200/v1/sys/leases/revoke

curl  -X POST \
      -H "Accept: application/json" -H "Content-Type: application/json" -H "X-Vault-Token: $token" \
      -d '{"url_lease_id":"kRmzOuXx6xbHcF","increment":6,"lease_id":null}' \
      http://localhost:8200/v1/sys/leases/renew

Expected behavior
A meaningful HTTP response.

Environment:

• Vault Server Version (retrieve with vault status): 1.12.2
• Vault CLI Version (retrieve with vault version): v1.12.2
• Server Operating System/Architecture: macOS Ventura 13.0.1

Additional context
Logs:

 [INFO]  http: panic serving 127.0.0.1:65074: interface conversion: interface {} is nil, not string
goroutine 73282 [running]:
net/http.(*conn).serve.func1()
        /opt/hostedtoolcache/go/1.19.3/x64/src/net/http/server.go:1850 +0xbf
panic({0x595efa0, 0xc001c84960})
        /opt/hostedtoolcache/go/1.19.3/x64/src/runtime/panic.go:890 +0x262
github.com/hashicorp/vault/vault.(*Core).handleCancelableRequest(0xc000890e00, {0x77566d8, 0xc001c845d0}, 0xc000245e00)
        /home/runner/work/vault/vault/vault/request_handling.go:628 +0x2434
github.com/hashicorp/vault/vault.(*Core).switchedLockHandleRequest(0xc000890e00, {0x77566d8, 0xc00092bd70}, 0xc000245e00, 0x20?)
        /home/runner/work/vault/vault/vault/request_handling.go:472 +0x539
github.com/hashicorp/vault/vault.(*Core).HandleRequest(...)
        /home/runner/work/vault/vault/vault/request_handling.go:433
github.com/hashicorp/vault/http.request(0x5e44920?, {0x7745388, 0xc00092bb60}, 0xc0019aed00, 0xc000245e00?)
        /home/runner/work/vault/vault/http/handler.go:910 +0x86

[ccapurso]

Thanks for bring this to our attention @ludovicianul! We have implemented a fix and will backport it to 1.10.x, 1.11.x, and 1.12.x.