🐛 capd: fix nil pointer in dockermachinepool controller

[chrischdi]

What this PR does / why we need it:

Fixes nil pointer which occurred e.g. here:

• https://prow.k8s.io/view/gs/kubernetes-jenkins/logs/periodic-cluster-api-e2e-mink8s-main/1812401250918993920
• CAPD logs: https://storage.googleapis.com/kubernetes-jenkins/logs/periodic-cluster-api-e2e-mink8s-main/1812401250918993920/artifacts/clusters/bootstrap/logs/capd-system/capd-controller-manager/capd-controller-manager-64d8bd4d45-77kh8/manager.log

{"ts":1720949295165.3877,"caller":"controller/controller.go:110","msg":"Observed a panic in reconciler: assignment to entry in nil map","controller":"dockermachinepool","controllerGroup":"infrastructure.cluster.x-k8s.io","controllerKind":"DockerMachinePool","DockerMachinePool":{"name":"autoscaler-qynhbr-mp-0-4hrqc","namespace":"autoscaler-wh9wa3"},"namespace":"autoscaler-wh9wa3","name":"autoscaler-qynhbr-mp-0-4hrqc","reconcileID":"5982a440-3d63-4817-b8fa-549b825f7753","v":0}
panic: assignment to entry in nil map [recovered]
	panic: assignment to entry in nil map

goroutine 325 [running]:
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile.func1()
	sigs.k8s.io/controller-runtime@v0.18.4/pkg/internal/controller/controller.go:111 +0x1e5
panic({0x1d48ca0?, 0x2370970?})
	runtime/panic.go:770 +0x132
sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers.(*DockerMachinePoolReconciler).propagateMachineDeleteAnnotation(0xc0004fa8c0, {0x23955e0, 0xc00062fb00}, 0xc000fd8290)
	sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers/dockermachinepool_controller_phases.go:326 +0x253
sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers.(*DockerMachinePoolReconciler).reconcileDockerMachines(0xc0004fa8c0, {0x23955e0, 0xc00062fb00}, 0xc0012041a0, 0xc000418848, 0xc001716c40)
	sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers/dockermachinepool_controller_phases.go:190 +0x112c
sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers.(*DockerMachinePoolReconciler).reconcileNormal(0xc0004fa8c0, {0x23955e0, 0xc00062fb00}, 0xc0012041a0, 0xc000418848, 0xc001716c40)
	sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers/dockermachinepool_controller.go:288 +0x13e
sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers.(*DockerMachinePoolReconciler).Reconcile(0xc0004fa8c0, {0x23955e0, 0xc00062f6e0}, {{{0xc0010b1410?, 0x3?}, {0xc0000585c0?, 0xc000accd10?}}})
	sigs.k8s.io/cluster-api/test/infrastructure/docker/exp/internal/controllers/dockermachinepool_controller.go:157 +0x8b0
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile(0x239c460?, {0x23955e0?, 0xc00062f6e0?}, {{{0xc0010b1410?, 0xb?}, {0xc0000585c0?, 0x0?}}})
	sigs.k8s.io/controller-runtime@v0.18.4/pkg/internal/controller/controller.go:114 +0xb7
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler(0xc000330840, {0x2395618, 0xc0004df950}, {0x1e0ab60, 0xc001935920})
	sigs.k8s.io/controller-runtime@v0.18.4/pkg/internal/controller/controller.go:311 +0x3bc
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem(0xc000330840, {0x2395618, 0xc0004df950})
	sigs.k8s.io/controller-runtime@v0.18.4/pkg/internal/controller/controller.go:261 +0x1be
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2()
	sigs.k8s.io/controller-runtime@v0.18.4/pkg/internal/controller/controller.go:222 +0x79
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2 in goroutine 102
	sigs.k8s.io/controller-runtime@v0.18.4/pkg/internal/controller/controller.go:218 +0x486

triage link

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

/area provider/infrastructure-docker

[chrischdi]

/cherry-pick release-1.7
/cherry-pick release-1.6

[k8s-infra-cherrypick-robot]

@chrischdi: once the present PR merges, I will cherry-pick it on top of release-1.7 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.7
/cherry-pick release-1.6

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[chrischdi]

/cherry-pick release-1.6

[k8s-infra-cherrypick-robot]

@chrischdi: once the present PR merges, I will cherry-pick it on top of release-1.6 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.6

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[sbueringer]

Thx!

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 634832ef6359ebd07dd24c747886fe5518b290f7

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: sbueringer

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [sbueringer]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[k8s-infra-cherrypick-robot]

@chrischdi: new pull request created: #10877

In response to this:

/cherry-pick release-1.7
/cherry-pick release-1.6

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

[k8s-infra-cherrypick-robot]

@chrischdi: new pull request created: #10878

In response to this:

/cherry-pick release-1.6

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.