`create cluster` fails when VPC CNI is configured to use both `iam.withOIDC` and `useDefaultPodIdentityAssociations`

[cPu1]

The following config results in a panic:

apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: test-cluster-3
  region: us-east-1
  version: '1.28'

addons:
- name: eks-pod-identity-agent
  version: v1.3.0
- name: vpc-cni
  version: v1.18.2
  useDefaultPodIdentityAssociations: true

iam:
  withOIDC: true

secretsEncryption:
  keyARN: arn:aws:kms:us-east-1:123456789:alias/test-kms

Stack trace -
2024-08-02 14:56:26 [ℹ]  creating addon
2024-08-02 14:56:27 [ℹ]  successfully created addon
2024-08-02 14:56:28 [ℹ]  "addonsConfig.autoApplyPodIdentityAssociations" is set to true; will lookup recommended pod identity configuration for "vpc-cni" addon
2024-08-02 14:56:30 [ℹ]  deploying stack "eksctl-test-cluster-3-addon-vpc-cni-podidentityrole-aws-node"
2024-08-02 14:56:30 [ℹ]  waiting for CloudFormation stack "eksctl-test-cluster-3-addon-vpc-cni-podidentityrole-aws-node"
2024-08-02 14:57:01 [ℹ]  waiting for CloudFormation stack "eksctl-test-cluster-3-addon-vpc-cni-podidentityrole-aws-node"
2024-08-02 14:57:02 [ℹ]  creating addon
2024-08-02 14:57:03 [ℹ]  successfully created addon
2024-08-02 14:57:04 [ℹ]  creating addon
2024-08-02 14:57:04 [ℹ]  successfully created addon
2024-08-02 14:57:05 [ℹ]  creating addon
2024-08-02 14:57:06 [ℹ]  successfully created addon
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x20 pc=0x1055303f8]

goroutine 187 [running]:
github.com/weaveworks/eksctl/pkg/actions/addon.(*Manager).Update(0x1400073f4a0, {0x107bc4e68, 0x10a3332e0}, 0x140005c2b40, {0x0, 0x0}, 0x15d3ef79800)
        github.com/weaveworks/eksctl/pkg/actions/addon/update.go:121 +0xeb8
github.com/weaveworks/eksctl/pkg/actions/addon.CreateAddonTasks.func3()
        github.com/weaveworks/eksctl/pkg/actions/addon/tasks.go:110 +0x90
github.com/weaveworks/eksctl/pkg/utils/tasks.(*GenericTask).Do(0x14000a2bd58, 0x0?)
        github.com/weaveworks/eksctl/pkg/utils/tasks/tasks.go:31 +0x34
github.com/weaveworks/eksctl/pkg/utils/tasks.doSingleTask(0x0?, {0x107b74ac0, 0x14000a2bd58})
        github.com/weaveworks/eksctl/pkg/utils/tasks/tasks.go:202 +0xc8
github.com/weaveworks/eksctl/pkg/utils/tasks.doSequentialTasks(0x1400061b4e0?, {0x1400061e980, 0x5, 0x1400022c160?})
        github.com/weaveworks/eksctl/pkg/utils/tasks/tasks.go:250 +0x6c
created by github.com/weaveworks/eksctl/pkg/utils/tasks.(*TaskTree).Do in goroutine 185
        github.com/weaveworks/eksctl/pkg/utils/tasks/tasks.go:158 +0x258

[artem-nefedov]

Not sure if related, but I found that ekctl 0.187.0 falsely complains in logs during create cluster when vpc-cni addon is specified without pod identity, but with attachPolicyARNs:

IRSA config is set for "vpc-cni" addon, but since OIDC is disabled on the cluster, eksctl cannot configure the requested permissions; the recommended way to provide IAM permissions for "vpc-cni" addon is via pod identity associations; after addon creation is completed, add all recommended policies to the config file, under addon.PodIdentityAssociations, and run eksctl update addon

The cluster config does have iam.withOIDC: true, and OIDC works without issues when cluster is created.