Distinguish if error occurd or if no matching prefix was found

[bruelea]

This PR fixes a panic that occurred if now matching parent prefix was found for a prefixclaim.

[gdask]

It looks fine.
A regression test was done:

apiVersion: netbox.dev/v1 kind: PrefixClaim metadata: labels: app.kubernetes.io/name: netbox-operator app.kubernetes.io/managed-by: kustomize name: prefixclaim-parentprefixselector-sample spec: tenant: "MY_TENANT" site: "DM-Akron" description: "some description" comments: "your comments" preserveInNetbox: true prefixLength: "/31" parentPrefixSelector: tenant: "MY_TENANT" family: "IPv4" environment: "Home" poolName: "Pool 1"

After the fix an error "no parent prefix found matching the parenPrefixSelector" is thrown instead of a panic.