[bug] nil pointer panic error if spec.core.kcm value is not set in custom Management object

[Algeran]

Describe the bug
I disabled creation of the default Management object by kcm controller and created the custom object. It mostly the same as the default one but without the spec.core values. Validation webhook allows to create it, but kcm controller starts failing and restarting with nil pointer panics on this line:
https://github.com/k0rdent/kcm/blob/v0.0.7/internal/controller/management_controller.go#L528

To Reproduce
Steps to reproduce the behavior:

1. bootstrap kcm controller with controller.createManagement: false
2. apply the custom management object:

   apiVersion: k0rdent.mirantis.com/v1alpha1
   kind: Management
   metadata:
     labels:
       k0rdent.mirantis.com/component: kcm
     name: kcm
   spec:
     providers:
     - name: k0smotron
     - name: cluster-api-provider-aws
     - name: cluster-api-provider-azure
     - name: cluster-api-provider-vsphere
     - name: cluster-api-provider-openstack
     - name: projectsveltos
     release: kcm-0-0-7
   

Expected behavior
Forbid to create objects without the .spec.core.kcm value or fill it with default values

Additional context