Submission of connect enabled task with no sidecar_service stanza causes panic

[shoenig]

Luckily Nomad agent continues operating, this is purely cosmetic.

$ cat foo.nomad
job "foo" {
  datacenters = ["dc1"]

  group "api" {
    network {
      mode = "bridge"
    }

    service {
      name = "count-api"
      connect {
	# sidecar_service {}
      }
    }
  }

  task "web" {
    driver = "docker"
    config {
      image = "hashicorpnomad/counter-api:v1"
    }
  }
}    

Logs

2020/04/09 14:26:33.621409 http: panic serving 127.0.0.1:40170: runtime error: invalid memory address or nil pointer dereference
goroutine 2404 [running]:
net/http.(*conn).serve.func1(0xc00003a6e0)
	/opt/google/go/src/net/http/server.go:1772 +0x139
panic(0x2784420, 0x4fc66f0)
	/opt/google/go/src/runtime/panic.go:973 +0x3e3
github.com/hashicorp/nomad/nomad/structs.(*ConsulSidecarService).Copy(0x0, 0x2c9ae40)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/structs/services.go:705 +0x26
github.com/hashicorp/nomad/nomad/structs.(*ConsulConnect).Copy(0xc00128a9a0, 0x0)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/structs/services.go:642 +0x3c
github.com/hashicorp/nomad/nomad/structs.(*Service).Copy(0xc00003a780, 0x1)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/structs/services.go:397 +0x203
github.com/hashicorp/nomad/nomad/structs.(*TaskGroup).Copy(0xc0003425a0, 0xc000342870)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/structs/structs.go:5251 +0x387
github.com/hashicorp/nomad/nomad/structs.(*Job).Copy(0xc0009cc5a0, 0x27cf9e0)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/structs/structs.go:3701 +0x221
github.com/hashicorp/nomad/nomad.(*Job).admissionValidators(0xc000126410, 0xc0009cc5a0, 0xc0009cc5a0, 0x0, 0x0, 0x0, 0x0)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/job_endpoint_hooks.go:75 +0x40
github.com/hashicorp/nomad/nomad.(*Job).admissionControllers(0xc000126410, 0xc0009cc5a0, 0x7, 0x34e7701, 0xc000c02660, 0x29e3920, 0xc000c02660, 0x2469cc0)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/job_endpoint_hooks.go:48 +0xa9
github.com/hashicorp/nomad/nomad.(*Job).Register(0xc000126410, 0xc000c02660, 0xc0000ad270, 0x0, 0x0)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/job_endpoint.go:93 +0x3b8
reflect.Value.call(0xc00087f440, 0xc00099c678, 0x13, 0x2dcd772, 0x4, 0xc0019df5d0, 0x3, 0x3, 0xc0000ad270, 0xc0019df628, ...)
	/opt/google/go/src/reflect/value.go:460 +0x8ab
reflect.Value.Call(0xc00087f440, 0xc00099c678, 0x13, 0xc0019df5d0, 0x3, 0x3, 0x8, 0x16, 0x16)
	/opt/google/go/src/reflect/value.go:321 +0xb4
net/rpc.(*service).call(0xc000a84e00, 0xc000126280, 0xc001ae25e0, 0x0, 0xc00011e600, 0xc000454c00, 0x29e3920, 0xc000c02660, 0x16, 0x2469cc0, ...)
	/opt/google/go/src/net/rpc/server.go:377 +0x17f
net/rpc.(*Server).ServeRequest(0xc000126280, 0x34e0e40, 0xc000a36740, 0xc000bfef30, 0xc00007ea80)
	/opt/google/go/src/net/rpc/server.go:498 +0x23e
github.com/hashicorp/nomad/nomad.(*Server).RPC(0xc000165200, 0x2ddbf29, 0xc, 0x29e3920, 0xc000c02600, 0x2469cc0, 0xc0000ad1d0, 0xc0006e8001, 0xc0000ad1d0)
	/home/hoenig/go/src/github.com/hashicorp/nomad/nomad/server.go:1517 +0xb9
github.com/hashicorp/nomad/command/agent.(*Agent).RPC(0xc0008421a0, 0x2ddbf29, 0xc, 0x29e3920, 0xc000c02600, 0x2469cc0, 0xc0000ad1d0, 0x0, 0x8)
	/home/hoenig/go/src/github.com/hashicorp/nomad/command/agent/agent.go:929 +0x7d
github.com/hashicorp/nomad/command/agent.(*HTTPServer).jobUpdate(0xc00099b630, 0x34c8700, 0xc000c025a0, 0xc0006e8000, 0x0, 0x0, 0x0, 0xc000b05970, 0x8, 0xc000b05930)
	/home/hoenig/go/src/github.com/hashicorp/nomad/command/agent/job_endpoint.go:426 +0x383
github.com/hashicorp/nomad/command/agent.(*HTTPServer).JobsRequest(0xc00099b630, 0x34c8700, 0xc000c025a0, 0xc0006e8000, 0x4d7fb6, 0x5e8f84f9, 0x25049324, 0x43298ff7d451)
	/home/hoenig/go/src/github.com/hashicorp/nomad/command/agent/job_endpoint.go:22 +0x84
github.com/hashicorp/nomad/command/agent.(*HTTPServer).wrap.func1(0x34c8700, 0xc000c025a0, 0xc0006e8000)
	/home/hoenig/go/src/github.com/hashicorp/nomad/command/agent/http.go:444 +0x176
net/http.HandlerFunc.ServeHTTP(0xc0003fcda0, 0x34c8700, 0xc000c025a0, 0xc0006e8000)
	/opt/google/go/src/net/http/server.go:2012 +0x44
net/http.(*ServeMux).ServeHTTP(0xc000745680, 0x34c8700, 0xc000c025a0, 0xc0006e8000)
	/opt/google/go/src/net/http/server.go:2387 +0x1a5
github.com/hashicorp/nomad/vendor/github.com/NYTimes/gziphandler.GzipHandlerWithOpts.func1.1(0x34cc780, 0xc0018aa620, 0xc0006e8000)
	/home/hoenig/go/src/github.com/hashicorp/nomad/vendor/github.com/NYTimes/gziphandler/gzip.go:269 +0x1e6
net/http.HandlerFunc.ServeHTTP(0xc000b96db0, 0x34cc780, 0xc0018aa620, 0xc0006e8000)
	/opt/google/go/src/net/http/server.go:2012 +0x44
net/http.serverHandler.ServeHTTP(0xc000ba8000, 0x34cc780, 0xc0018aa620, 0xc0006e8000)
	/opt/google/go/src/net/http/server.go:2807 +0xa3
net/http.(*conn).serve(0xc00003a6e0, 0x34e0b80, 0xc000a36380)
	/opt/google/go/src/net/http/server.go:1895 +0x86c
created by net/http.(*Server).Serve
	/opt/google/go/src/net/http/server.go:2933 +0x35c
    2020-04-09T14:26:34.530-0600 [DEBUG] http: request complete: method=GET path=/v1/agent/health?type=server duration=476.2µs
    2020-04-09T14:26:38.974-0600 [DEBUG] http: request complete: method=GET path=/v1/agent/health?type=client duration=284.607µs

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