SSH banner check without empty and unused user and password causes panic

[agross]

Describe the bug

endpoints:
  - name: Hetzner StorageBox SSH
    group: Infrastructure
    url: ssh://u497426.your-storagebox.de:23
    interval: 10s
    conditions:
      - "[CONNECTED] == true"

What do you see?

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0xb0d722]

goroutine 373 [running]:
github.com/TwiN/gatus/v5/config/endpoint.(*Endpoint).call(0xc000241e60, 0xc000000620)
        /app/config/endpoint/endpoint.go:501 +0xae2
github.com/TwiN/gatus/v5/config/endpoint.(*Endpoint).EvaluateHealthWithContext(0xc000241e60, 0x0)
        /app/config/endpoint/endpoint.go:326 +0x3b9
github.com/TwiN/gatus/v5/config/endpoint.(*Endpoint).EvaluateHealth(...)
        /app/config/endpoint/endpoint.go:286
github.com/TwiN/gatus/v5/watchdog.executeEndpoint(0xc000241e60, 0xc000000000, {0x240f6a0, 0x0, 0x0})
        /app/watchdog/endpoint.go:49 +0x1f8
github.com/TwiN/gatus/v5/watchdog.monitorEndpoint(0xc000241e60, 0xc000000000, {0x240f6a0, 0x0, 0x0}, {0x186beb0, 0xc0000a9450})
        /app/watchdog/endpoint.go:17 +0x66
created by github.com/TwiN/gatus/v5/watchdog.Monitor in goroutine 1
        /app/watchdog/watchdog.go:42 +0x210

What do you expect to see?

Gatus not crashing.

List the steps that must be taken to reproduce this issue

1. Add check like above

Version

5.27.1

Additional information

No response

[agross]

Interestingly, it works when the ssh: key is configured with an empty username and password.

Is that intuitive? I'd say it's not, given the docs stating that username is optional and password is only required if the username is provided.

endpoints:
  - name: Hetzner StorageBox SSH
    group: Infrastructure
    url: ssh://u497426.your-storagebox.de:23
    ssh:
      username: ""
      password: ""    
    interval: 10s
    conditions:
      - "[CONNECTED] == true"

[TwiN]

@agross This looks like a bug. I'll fix it in a couple minutes.

[TwiN]

@agross Once the build for #1358 is published, can you try the latest image to check if it fixed your issue?

[agross]

latest works 👍🏻

[TwiN]

Thank you for verifying it!