v0.10.0-rc.0 stacktrace when during cluster deletion

[huxcrux]

/kind bug

What steps did you take and what happened:
During cluster deletion my CAPO controller-manager crashes with the following stacktrace:

I0412 11:45:50.916394       1 openstackcluster_controller.go:260] "Deleting Bastion" controller="openstackcluster" controllerGroup="infrastructure.cluster.x-k8s.io" controllerKind="OpenStackCluster" OpenStackCluster="default/hux-lab1" namespace="default" name="hux-lab1" reconcileID="2b4f4d91-fc50-4a8a-b2f8-2cb3db96d50c" cluster="hux-lab1"
I0412 11:45:51.204917       1 controller.go:115] "Observed a panic in reconciler: runtime error: invalid memory address or nil pointer dereference" controller="openstackcluster" controllerGroup="infrastructure.cluster.x-k8s.io" controllerKind="OpenStackCluster" OpenStackCluster="default/hux-lab1" namespace="default" name="hux-lab1" reconcileID="2b4f4d91-fc50-4a8a-b2f8-2cb3db96d50c"
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=0x60 pc=0x1b912b0]

goroutine 425 [running]:
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile.func1()
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:116 +0x1e5
panic({0x1db33e0?, 0x3646f90?})
	/usr/local/go/src/runtime/panic.go:770 +0x132
sigs.k8s.io/cluster-api-provider-openstack/controllers.bastionToInstanceSpec(0xc000a56f08, 0xc000c12820?)
	/workspace/controllers/openstackcluster_controller.go:563 +0xb0
sigs.k8s.io/cluster-api-provider-openstack/controllers.deleteBastion(0xc0009fbd70, 0xc000c12820, 0xc000a56f08)
	/workspace/controllers/openstackcluster_controller.go:297 +0x2db
sigs.k8s.io/cluster-api-provider-openstack/controllers.(*OpenStackClusterReconciler).reconcileDelete(0xc000547740, {0x242d758, 0xc000e81770}, 0xc0009fbd70, 0xc000c12820, 0xc000a56f08)
	/workspace/controllers/openstackcluster_controller.go:160 +0x2b2
sigs.k8s.io/cluster-api-provider-openstack/controllers.(*OpenStackClusterReconciler).Reconcile(0xc000547740, {0x242d758, 0xc000e81770}, {{{0xc000b46040?, 0x0?}, {0xc000b46088?, 0xc00089dd50?}}})
	/workspace/controllers/openstackcluster_controller.go:126 +0x6cc
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile(0x2432cc8?, {0x242d758?, 0xc000e81770?}, {{{0xc000b46040?, 0xb?}, {0xc000b46088?, 0x0?}}})
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:119 +0xb7
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc0006faaa0, {0x242d790, 0xc000575b80}, {0x1e7dc40, 0xc000329400})
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:316 +0x3bc
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc0006faaa0, {0x242d790, 0xc000575b80})
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:266 +0x1c9
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2()
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:227 +0x79
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2 in goroutine 200
	/go/pkg/mod/sigs.k8s.io/controller-runtime@v0.16.3/pkg/internal/controller/controller.go:223 +0x50c

openstackcluster:

apiVersion: infrastructure.cluster.x-k8s.io/v1beta1
kind: OpenStackCluster
metadata:
  creationTimestamp: "2024-04-12T11:12:54Z"
  deletionGracePeriodSeconds: 0
  deletionTimestamp: "2024-04-12T11:43:04Z"
  finalizers:
  - openstackcluster.infrastructure.cluster.x-k8s.io
  generation: 4
  labels:
    cluster.x-k8s.io/cluster-name: hux-lab1
  name: hux-lab1
  namespace: default
  ownerReferences:
  - apiVersion: cluster.x-k8s.io/v1beta1
    blockOwnerDeletion: true
    controller: true
    kind: Cluster
    name: hux-lab1
    uid: 28be47df-1ba5-417a-81f5-84916aca2a82
  resourceVersion: "10137"
  uid: 38e38891-bbe4-4e45-9161-129ce22ad71c
spec:
  apiServerLoadBalancer:
    additionalPorts:
    - [REDACTED]
    allowedCIDRs:
    - [REDACTED]
    enabled: true
  controlPlaneAvailabilityZones:
  - sto1
  - sto2
  - sto3
  controlPlaneEndpoint:
    host: [REDACTED]
    port: 6443
  externalNetwork:
    id: 600b8501-78cb-4155-9c9f-23dfcba88828
  identityRef:
    cloudName: elastx
    name: hux-lab1-cloud-config
  managedSecurityGroups:
    allNodesSecurityGroupRules:
    - description: Allow BGP traffic
      direction: ingress
      etherType: IPv4
      name: BGP (Calico)
      portRangeMax: 179
      portRangeMin: 179
      protocol: tcp
      remoteManagedGroups:
      - controlplane
      - worker
    - description: Allow IP-in-IP traffic
      direction: ingress
      etherType: IPv4
      name: IP-in-IP (calico)
      protocol: "4"
      remoteManagedGroups:
      - controlplane
      - worker
    allowAllInClusterTraffic: true
  managedSubnets:
  - cidr: 10.128.0.0/22
    dnsNameservers:
    - [REDACTED]
status:
  apiServerLoadBalancer:
    allowedCIDRs:
    - [REDACTED]
    id: e01a7390-f43c-4c5f-b693-e3a42a1bdbb5
    internalIP: 10.128.2.205
    ip: [REDACTED]
    loadBalancerNetwork:
      id: ""
      name: ""
    name: k8s-clusterapi-cluster-default-hux-lab1-kubeapi
  controlPlaneSecurityGroup:
    id: bb9e434c-64f4-40e0-8a0d-d0ba6ddfde71
    name: k8s-cluster-default-hux-lab1-secgroup-controlplane
  externalNetwork:
    id: 600b8501-78cb-4155-9c9f-23dfcba88828
    name: elx-public1
  failureDomains:
    sto1:
      controlPlane: true
    sto2:
      controlPlane: true
    sto3:
      controlPlane: true
  network:
    id: ae6b5ea2-a851-4c09-a12b-9623ffae0da0
    name: k8s-clusterapi-cluster-default-hux-lab1
    subnets:
    - cidr: 10.128.0.0/22
      id: f0bfc3d3-26e6-4fec-a8be-e8f5a3dd7179
      name: k8s-clusterapi-cluster-default-hux-lab1
  ready: true
  router:
    id: 296b2430-afd8-49d9-b42f-b2edfe833927
    ips:
    - [REDACTED]
    name: k8s-clusterapi-cluster-default-hux-lab1
  workerSecurityGroup:
    id: 162ad19c-b8ea-4935-8510-50eac441839d
    name: k8s-cluster-default-hux-lab1-secgroup-worker

What did you expect to happen:
The cluster to be deleted

Anything else you would like to add:
[Miscellaneous information that will assist in solving the issue.]

Environment:

• Cluster API Provider OpenStack version (Or git rev-parse HEAD if manually built): 0.10.0-rc.0
• Cluster-API version: v1.6.3
• OpenStack version: Ussuri
• Minikube/KIND version: kind v0.22.0
• Kubernetes version (use kubectl version): 1.29.1
• OS (e.g. from /etc/os-release): Ubuntu 22.04