Fixes segfault when VPC CNI is disabled

[EmmEff]

This PR resolves a segfault that occurs when VPC CNI is disabled and a minimal cluster.yaml is used:

apiVersion: eksctl.io/v1alpha5
kind: ClusterConfig

metadata:
  name: my-calico-cluster
  region: us-east-2

addonsConfig:
  disableDefaultAddons: true

addons:
  - name: kube-proxy
  - name: coredns

[github-actions]

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