dutagent config validation crash

[AtomicFS]

Describe the bug
When running dutagent --check-config -c <PATH_TO_CONFIG>, the program crashes with panic on valid config, if GPIO module is used.

When running against non-GPIO config or invalid config, it exists properly as expected.

Expected behavior
Just run validation and exit. Exactly as described in the help:

Only validate the provided DUT configuration, not starting the service

Version
latest main (commit 268bb80)

Steps to reproduce

• Run dutagent --check-config -c <PATH_TO_VALID_CONFIG>
  For example:
• Run dutagent --check-config -c pkg/module/gpio/gpio-example-cfg.yml

Involved Components (please complete / adapt the following information):

• dutagent running locally

DUT Agent YAML Configuration
Any valid config

I have used:

---
version: 0
devices:
  fwci-dutctl-tester:
    desc: "A fwci dutctl tester"
    cmds:
      power:
        desc: "Power switch"
        uses:
          - module: gpio-switch
            main: true
            with:
              pin: 26
              initial: off
      serial:
        desc: |
          Basic demo of the Serial module: After the DUT is powered on, use Serial
          as the main module to wait for magic strings in the DUT's boot log.
        uses:
          - module: serial
            main: true
            with:
              port: /home/oscar/ttyS2
              baudrate: 115200

Additional context
It outputs Configuration is valid and then crashes.

2026/03/03 13:31:44 Configuration is valid
2026/03/03 13:31:44 GRACEFUL SHUTDOWN: De-init modules
2026/03/03 13:31:44 gpio.Switch module: Deinit called
2026/03/03 13:31:44 Recovered from panic: runtime error: invalid memory address or nil pointer dereference
2026/03/03 13:31:44 GRACEFUL SHUTDOWN: De-init modules
2026/03/03 13:31:44 gpio.Switch module: Deinit called
panic: runtime error: invalid memory address or nil pointer dereference [recovered, repanicked]
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x94a55b]

goroutine 1 [running]:
github.com/BlindspotSoftware/dutctl/pkg/module/gpio.(*Switch).Deinit(0x31b463b29260)
	.../dutctl/pkg/module/gpio/gpio.go:261 +0x7b
github.com/BlindspotSoftware/dutctl/internal/dutagent.Deinit(0x31b463be5c80)
	.../dutctl/internal/dutagent/init.go:84 +0x23d
main.(*agent).cleanup(0x31b463b71810, 0x1)
	.../dutctl/cmds/dutagent/dutagent.go:100 +0x31
main.(*agent).start.func1()
	.../dutctl/cmds/dutagent/dutagent.go:244 +0x98
panic({0xb6ab80?, 0x12d9d40?})
	/usr/lib/go/src/runtime/panic.go:860 +0x13a
github.com/BlindspotSoftware/dutctl/pkg/module/gpio.(*Switch).Deinit(0x31b463b29260)
	.../dutctl/pkg/module/gpio/gpio.go:261 +0x7b
github.com/BlindspotSoftware/dutctl/internal/dutagent.Deinit(0x31b463be5c80)
	.../dutctl/internal/dutagent/init.go:84 +0x23d
main.(*agent).cleanup(0x31b463b71810, 0x0)
	.../dutctl/cmds/dutagent/dutagent.go:100 +0x31
main.(*agent).start(0x31b463b71810)
	.../dutctl/cmds/dutagent/dutagent.go:258 +0x1e9
main.main()
	.../dutctl/cmds/dutagent/dutagent.go:298 +0x45

Suggestions

• you should run dutagent --check-config -c on all of the example config files as part of testing
• you should use the same code that does config validation on startup as the one that runs when --check-config is used (I actually do not know how it is done internally right now)