Setting HorizontalRunnerAutoscaler metrics scaleDownThreshold to 0 cause a segmentation fault

Checks

• I've already read https://github.com/actions-runner-controller/actions-runner-controller/blob/master/TROUBLESHOOTING.md and I'm sure my issue is not covered in the troubleshooting guide.
• I'm not using a custom entrypoint in my runner image

Controller Version

0.21.1

Helm Chart Version

0.21.0

CertManager Version

1.9.1

Deployment Method

ArgoCD

cert-manager installation

• Yes
• Yes

Checks

• This isn't a question or user support case (For Q&A and community support, go to Discussions. It might also be a good idea to contract with any of contributors and maintainers if your business is so critical and therefore you need priority support
• I've read releasenotes before submitting this issue and I'm sure it's not due to any recently-introduced backward-incompatible changes
• My actions-runner-controller version (v0.x.y) does support the feature
• I've already upgraded ARC (including the CRDs, see charts/actions-runner-controller/docs/UPGRADING.md for details) to the latest and it didn't fix the issue
• I've migrated to the workflow job webhook event (if you using webhook driven scaling)

Resource Definitions

---
apiVersion: actions.summerwind.dev/v1alpha1
kind: HorizontalRunnerAutoscaler
metadata:
  name: infra-runner-large
spec:
  scaleTargetRef:
    name: infra-runner-large
  scaleDownDelaySecondsAfterScaleOut: 900
  minReplicas: 0
  maxReplicas: 30
  metrics:
  - type: PercentageRunnersBusy
    scaleUpThreshold: '1'
    scaleDownThreshold: '0'
    scaleUpFactor: '1.5'
    scaleDownFactor: '0.9'

To Reproduce

1- Create the resource and corresponding runnerdeployment
2- The controller should crash

Describe the bug

The container crash with the a seg fault log.

Describe the expected behavior

The error should be more verbose and instead of crashing with a segfault tell us that the value is not valid.

Whole Controller Logs

2022-12-01T10:18:07Z	INFO	controller-runtime.metrics	Metrics server is starting to listen	{"addr": "127.0.0.1:8080"}
2022-12-01T10:18:07Z	INFO	actions-runner-controller	Initializing actions-runner-controller	{"version": "v0.26.0", "default-scale-down-delay": "10m0s", "sync-period": "1m0s", "default-runner-image": "summerwind/actions-runner:latest", "default-docker-image": "docker:dind", "common-runnner-labels": null, "leader-election-enabled": true, "leader-election-id": "actions-runner-controller", "watch-namespace": ""}
2022-12-01T10:18:07Z	INFO	controller-runtime.builder	Registering a mutating webhook	{"GVK": "actions.summerwind.dev/v1alpha1, Kind=Runner", "path": "/mutate-actions-summerwind-dev-v1alpha1-runner"}
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Registering webhook	{"path": "/mutate-actions-summerwind-dev-v1alpha1-runner"}
2022-12-01T10:18:07Z	INFO	controller-runtime.builder	Registering a validating webhook	{"GVK": "actions.summerwind.dev/v1alpha1, Kind=Runner", "path": "/validate-actions-summerwind-dev-v1alpha1-runner"}
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Registering webhook	{"path": "/validate-actions-summerwind-dev-v1alpha1-runner"}
2022-12-01T10:18:07Z	INFO	controller-runtime.builder	Registering a mutating webhook	{"GVK": "actions.summerwind.dev/v1alpha1, Kind=RunnerDeployment", "path": "/mutate-actions-summerwind-dev-v1alpha1-runnerdeployment"}
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Registering webhook	{"path": "/mutate-actions-summerwind-dev-v1alpha1-runnerdeployment"}
2022-12-01T10:18:07Z	INFO	controller-runtime.builder	Registering a validating webhook	{"GVK": "actions.summerwind.dev/v1alpha1, Kind=RunnerDeployment", "path": "/validate-actions-summerwind-dev-v1alpha1-runnerdeployment"}
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Registering webhook	{"path": "/validate-actions-summerwind-dev-v1alpha1-runnerdeployment"}
2022-12-01T10:18:07Z	INFO	controller-runtime.builder	Registering a mutating webhook	{"GVK": "actions.summerwind.dev/v1alpha1, Kind=RunnerReplicaSet", "path": "/mutate-actions-summerwind-dev-v1alpha1-runnerreplicaset"}
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Registering webhook	{"path": "/mutate-actions-summerwind-dev-v1alpha1-runnerreplicaset"}
2022-12-01T10:18:07Z	INFO	controller-runtime.builder	Registering a validating webhook	{"GVK": "actions.summerwind.dev/v1alpha1, Kind=RunnerReplicaSet", "path": "/validate-actions-summerwind-dev-v1alpha1-runnerreplicaset"}
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Registering webhook	{"path": "/validate-actions-summerwind-dev-v1alpha1-runnerreplicaset"}
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Registering webhook	{"path": "/mutate-runner-set-pod"}
2022-12-01T10:18:07Z	INFO	actions-runner-controller	starting manager
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook.webhooks	Starting webhook server
2022-12-01T10:18:07Z	INFO	Starting server	{"path": "/metrics", "kind": "metrics", "addr": "127.0.0.1:8080"}
2022-12-01T10:18:07Z	INFO	controller-runtime.certwatcher	Updated current TLS certificate
2022-12-01T10:18:07Z	INFO	controller-runtime.webhook	Serving webhook server	{"host": "", "port": 9443}
2022-12-01T10:18:07Z	INFO	controller-runtime.certwatcher	Starting certificate watcher
I1201 10:18:07.324149       1 leaderelection.go:248] attempting to acquire leader lease github-runner/actions-runner-controller...
I1201 10:18:24.743082       1 leaderelection.go:258] successfully acquired lease github-runner/actions-runner-controller
2022-12-01T10:18:24Z	DEBUG	events	Normal	{"object": {"kind":"Lease","namespace":"github-runner","name":"actions-runner-controller","uid":"0a14c8b7-f528-4b94-b8a5-e27d4f984830","apiVersion":"coordination.k8s.io/v1","resourceVersion":"576625600"}, "reason": "LeaderElection", "message": "github-runner-actions-runner-controller-69f7468d5d-gwkp2_3d63d60a-867f-4e55-a434-6047862c5f4e became leader"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runner-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "Runner", "source": "kind source: *v1alpha1.Runner"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runner-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "Runner", "source": "kind source: *v1.Pod"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "runner-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "Runner"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerreplicaset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerReplicaSet", "source": "kind source: *v1alpha1.RunnerReplicaSet"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerreplicaset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerReplicaSet", "source": "kind source: *v1alpha1.Runner"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerSet", "source": "kind source: *v1alpha1.RunnerSet"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerSet", "source": "kind source: *v1.StatefulSet"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "runnerset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerSet"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "runnerreplicaset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerReplicaSet"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerpersistentvolume-controller", "controllerGroup": "", "controllerKind": "PersistentVolume", "source": "kind source: *v1.PersistentVolume"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "runnerpersistentvolume-controller", "controllerGroup": "", "controllerKind": "PersistentVolume"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerdeployment-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerDeployment", "source": "kind source: *v1alpha1.RunnerDeployment"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "horizontalrunnerautoscaler-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "HorizontalRunnerAutoscaler", "source": "kind source: *v1alpha1.HorizontalRunnerAutoscaler"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "horizontalrunnerautoscaler-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "HorizontalRunnerAutoscaler"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerdeployment-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerDeployment", "source": "kind source: *v1alpha1.RunnerReplicaSet"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerpersistentvolumeclaim-controller", "controllerGroup": "", "controllerKind": "PersistentVolumeClaim", "source": "kind source: *v1.PersistentVolumeClaim"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "runnerpersistentvolumeclaim-controller", "controllerGroup": "", "controllerKind": "PersistentVolumeClaim"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "runnerdeployment-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerDeployment"}
2022-12-01T10:18:24Z	INFO	Starting EventSource	{"controller": "runnerpod-controller", "controllerGroup": "", "controllerKind": "Pod", "source": "kind source: *v1.Pod"}
2022-12-01T10:18:24Z	INFO	Starting Controller	{"controller": "runnerpod-controller", "controllerGroup": "", "controllerKind": "Pod"}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "runnerpod-controller", "controllerGroup": "", "controllerKind": "Pod", "worker count": 1}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "runnerpersistentvolumeclaim-controller", "controllerGroup": "", "controllerKind": "PersistentVolumeClaim", "worker count": 1}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "runnerreplicaset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerReplicaSet", "worker count": 1}
2022-12-01T10:18:24Z	DEBUG	actions-runner-controller.runnerreplicaset	Skipped reconcilation because owner is not synced yet	{"runnerreplicaset": "github-runner/infra-runner-small-8g8x6", "owner": "github-runner/infra-runner-small-8g8x6-nrt5j", "pods": null}
2022-12-01T10:18:24Z	DEBUG	actions-runner-controller.runnerreplicaset	Skipped reconcilation because owner is not synced yet	{"runnerreplicaset": "github-runner/infra-runner-large-vvr82", "owner": "github-runner/infra-runner-large-vvr82-tw9dd", "pods": null}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "runner-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "Runner", "worker count": 1}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "horizontalrunnerautoscaler-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "HorizontalRunnerAutoscaler", "worker count": 1}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "runnerpersistentvolume-controller", "controllerGroup": "", "controllerKind": "PersistentVolume", "worker count": 1}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "runnerdeployment-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerDeployment", "worker count": 1}
2022-12-01T10:18:24Z	INFO	Starting workers	{"controller": "runnerset-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "RunnerSet", "worker count": 1}
2022-12-01T10:18:24Z	DEBUG	controller-runtime.webhook.webhooks	received request	{"webhook": "/mutate-runner-set-pod", "UID": "80a4fbdd-f0dc-433e-8ca9-2b07ccf6cb24", "kind": "/v1, Kind=Pod", "resource": {"group":"","version":"v1","resource":"pods"}}
2022-12-01T10:18:24Z	DEBUG	controller-runtime.webhook.webhooks	received request	{"webhook": "/mutate-actions-summerwind-dev-v1alpha1-runner", "UID": "9fe8c841-2f2e-4bca-a797-df88005f3a14", "kind": "actions.summerwind.dev/v1alpha1, Kind=Runner", "resource": {"group":"actions.summerwind.dev","version":"v1alpha1","resource":"runners"}}
2022-12-01T10:18:24Z	DEBUG	controller-runtime.webhook.webhooks	wrote response	{"webhook": "/mutate-actions-summerwind-dev-v1alpha1-runner", "code": 200, "reason": "", "UID": "9fe8c841-2f2e-4bca-a797-df88005f3a14", "allowed": true}
2022-12-01T10:18:24Z	DEBUG	controller-runtime.webhook.webhooks	received request	{"webhook": "/validate-actions-summerwind-dev-v1alpha1-runner", "UID": "0016d3ca-cdcc-4163-b770-5fcea23c58b8", "kind": "actions.summerwind.dev/v1alpha1, Kind=Runner", "resource": {"group":"actions.summerwind.dev","version":"v1alpha1","resource":"runners"}}
2022-12-01T10:18:24Z	INFO	runner-resource	validate resource to be created	{"name": "infra-runner-medium-hvb2t-jbhjp"}
2022-12-01T10:18:24Z	DEBUG	controller-runtime.webhook.webhooks	wrote response	{"webhook": "/validate-actions-summerwind-dev-v1alpha1-runner", "code": 200, "reason": "", "UID": "0016d3ca-cdcc-4163-b770-5fcea23c58b8", "allowed": true}
2022-12-01T10:18:25Z	DEBUG	actions-runner-controller.runnerreplicaset	Created replica(s)	{"runnerreplicaset": "github-runner/infra-runner-medium-hvb2t", "lastSyncTime": null, "effectiveTime": "<nil>", "templateHashDesired": "78d4d4cdc6", "replicasDesired": 1, "replicasPending": 0, "replicasRunning": 0, "replicasMaybeRunning": 0, "templateHashObserved": [], "created": 1}
2022-12-01T10:18:25Z	DEBUG	actions-runner-controller.runnerreplicaset	Skipped reconcilation because owner is not synced yet	{"runnerreplicaset": "github-runner/infra-runner-medium-hvb2t", "owner": "github-runner/infra-runner-medium-hvb2t-jbhjp", "pods": null}
2022-12-01T10:18:25Z	DEBUG	controller-runtime.webhook.webhooks	wrote response	{"webhook": "/mutate-runner-set-pod", "code": 200, "reason": "", "UID": "80a4fbdd-f0dc-433e-8ca9-2b07ccf6cb24", "allowed": true}
2022-12-01T10:18:25Z	INFO	Observed a panic in reconciler: runtime error: invalid memory address or nil pointer dereference	{"controller": "horizontalrunnerautoscaler-controller", "controllerGroup": "actions.summerwind.dev", "controllerKind": "HorizontalRunnerAutoscaler", "horizontalRunnerAutoscaler": {"name":"infra-runner-large","namespace":"github-runner"}, "namespace": "github-runner", "name": "infra-runner-large", "reconcileID": "8b7d5e23-31c0-45a7-a648-e9cc3e817a7b"}
panic: runtime error: invalid memory address or nil pointer dereference [recovered]
	panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x144ab8b]

goroutine 531 [running]:
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile.func1()
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.3/pkg/internal/controller/controller.go:118 +0x1f4
panic({0x1617ee0, 0x263f760})
	/usr/local/go/src/runtime/panic.go:884 +0x212
github.com/actions-runner-controller/actions-runner-controller/controllers.(*HorizontalRunnerAutoscalerReconciler).suggestReplicasByPercentageRunnersBusy(_, _, {{0xc00046a210, 0x12}, {0x183f9f5, 0x10}, {0x0, 0x0}, {0x0, 0x0}, ...}, ...)
	/workspace/controllers/autoscaling.go:393 +0xacb
github.com/actions-runner-controller/actions-runner-controller/controllers.(*HorizontalRunnerAutoscalerReconciler).suggestDesiredReplicas(_, _, {{0xc00046a210, 0x12}, {0x183f9f5, 0x10}, {0x0, 0x0}, {0x0, 0x0}, ...}, ...)
	/workspace/controllers/autoscaling.go:55 +0x308
github.com/actions-runner-controller/actions-runner-controller/controllers.(*HorizontalRunnerAutoscalerReconciler).computeReplicasWithCache(_, _, {{_, _}, _}, {_, _, _}, {{0xc00046a210, 0x12}, ...}, ...)
	/workspace/controllers/horizontalrunnerautoscaler_controller.go:473 +0xd8
github.com/actions-runner-controller/actions-runner-controller/controllers.(*HorizontalRunnerAutoscalerReconciler).reconcile(_, {_, _}, {{{_, _}, {_, _}}}, {{0x1a9b228, 0xc00160f6b0}, 0x0}, ...)
	/workspace/controllers/horizontalrunnerautoscaler_controller.go:319 +0x22b
github.com/actions-runner-controller/actions-runner-controller/controllers.(*HorizontalRunnerAutoscalerReconciler).Reconcile(0xc00011fec0, {0x1a98998?, 0xc00160f680}, {{{0xc000589b30, 0xd}, {0xc000571380, 0x12}}})
	/workspace/controllers/horizontalrunnerautoscaler_controller.go:100 +0x98c
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile(0x1a988f0?, {0x1a98998?, 0xc00160f680?}, {{{0xc000589b30?, 0x175eea0?}, {0xc000571380?, 0x4045d4?}}})
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.3/pkg/internal/controller/controller.go:121 +0xc8
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc000432960, {0x1a988f0, 0xc000552cc0}, {0x16891c0?, 0xc000b08b40?})
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.3/pkg/internal/controller/controller.go:320 +0x33c
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc000432960, {0x1a988f0, 0xc000552cc0})
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.3/pkg/internal/controller/controller.go:273 +0x1d9
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2()
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.3/pkg/internal/controller/controller.go:234 +0x85
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.12.3/pkg/internal/controller/controller.go:230 +0x333

Whole Runner Pod Logs

irrelevant

Additional Context

No response

Start by reproducing the crash with the HorizontalRunnerAutoscaler resource definition shown, focusing on the horizontalrunnerautoscaler-controller entry point named in the logs. Trace handling of the PercentageRunnersBusy metric and its scaleDownThreshold value; done means the invalid value produces a clear validation error instead of a segmentation fault, with a regression test if the relevant test location is found.