panic on nats server report connections with non-$SYS account

[MauriceVanVeen]

Defect

Versions of nats-server and affected client libraries used:

• nats-server 2.9.14
• nats-box 0.13.4

OS/Container environment:

• Kubernetes with official Helm chart

Steps or code to reproduce the issue:

Tried reproducing this in a similar 3-node setup on Kubernetes, but sadly wasn't able to.

Normally, when doing a nats server report connections with a user under $SYS this command always successfully returns a report in the CLI. However, when running this with a non-$SYS account, this command may sometimes succeed, and other times it will lead into an error message in the CLI:

nats: error: server request failed, ensure the account used has system privileges and appropriate permissions

When running this command quite rapidly after each other, it sometimes will result in a panic. (Although I'm not quite sure if it's even related to running this quickly, or if it's a race condition.)

The following panic happened:

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x38 pc=0x76acd4]

goroutine 178036893 [running]:
github.com/nats-io/nats-server/v2/server.(*serviceExport).setResponseThresholdTimer(...)
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/accounts.go:2227
github.com/nats-io/nats-server/v2/server.(*Account).addRespServiceImport(0xc000ba5440, 0xc000ba58c0, {0xc006c1abd0, 0x26}, 0xc003292090, 0x0, 0x0)
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/accounts.go:2347 +0x2f4
github.com/nats-io/nats-server/v2/server.(*client).setupResponseServiceImport(0xc0042f6600, 0xc002456d68?, 0xc003292090, 0x80?, 0xc002456df0?)
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/client.go:3724 +0x7f
github.com/nats-io/nats-server/v2/server.(*client).processServiceImport(0xc0042f6600, 0xc003292090, 0xc000ba58c0, {0xc00043004f, 0x100, 0x1b1})
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/client.go:3896 +0x44a
github.com/nats-io/nats-server/v2/server.(*Account).addServiceImportSub.func1(0x0?, 0x0?, 0x0?, {0x0?, 0x0?}, {0x0?, 0x0?}, {0xc00043004f, 0x100, 0x1b1})
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/accounts.go:1965 +0x32
github.com/nats-io/nats-server/v2/server.(*client).deliverMsg(0xc0042f6600, 0x0, 0xc002783140, 0x0?, {0xc000430005, 0x1a, 0x1fb}, {0xc000430020, 0x26, 0x1e0}, ...)
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/client.go:3192 +0xb89
github.com/nats-io/nats-server/v2/server.(*client).processMsgResults(0xc0042f6600, 0xc000ba58c0, 0xc001cf2330, {0xc00043004f, 0x100, 0x1b1}, {0x0, 0x0, 0x0?}, {0xc000430005, ...}, ...)
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/client.go:4239 +0xb10
github.com/nats-io/nats-server/v2/server.(*client).processInboundClientMsg(0xc0042f6600, {0xc00043004f, 0x100, 0x1b1})
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/client.go:3660 +0xaa8
github.com/nats-io/nats-server/v2/server.(*client).processInboundMsg(0xc0042f6600?, {0xc00043004f?, 0x48?, 0x1fb?})
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/client.go:3507 +0x3d
github.com/nats-io/nats-server/v2/server.(*client).parse(0xc0042f6600, {0xc000430000, 0x14f, 0x200})
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/parser.go:497 +0x210a
github.com/nats-io/nats-server/v2/server.(*client).readLoop(0xc0042f6600, {0x0, 0x0, 0x0})
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/client.go:1238 +0xf36
github.com/nats-io/nats-server/v2/server.(*Server).createClient.func1()
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/server.go:2654 +0x29
created by github.com/nats-io/nats-server/v2/server.(*Server).startGoRoutine
	/home/travis/gopath/src/github.com/nats-io/nats-server/server/server.go:3083 +0x85

Expected result:

Consistently return data that can be shown in the CLI report.

Actual result:

May panic a server, making it restart.