policy-controller: fix empty values

[walnuts1018]

Description of the change

This PR fixes the issue where only the key is output when the value is not provided for some fields such as .Values.annotations and .Values.webhook.podDisruptionBudget.maxUnavailable.

Existing or Associated Issue(s)

Additional Information

The state in which only the key is output, such as annotations: , is not syntactically correct in yaml, so lint tools such as kubeconform output an error.
In this PR, the position of the conditional branch has been slightly changed so that if value is not specified, key is also not output.

$ helm install policy-controller sigstore/policy-controller -n policy-controller --dry-run > old.yaml
$ helm install policy-controller ./charts/policy-controller -n policy-controller --dry-run > new.yaml
$ dyff between .\old.yaml .\new.yaml

old.yaml:

...
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: policy-controller-webhook
  labels:
    helm.sh/chart: policy-controller-0.7.0
    app.kubernetes.io/name: policy-controller
    app.kubernetes.io/instance: policy-controller
    app.kubernetes.io/version: "0.8.2"
    app.kubernetes.io/managed-by: Helm
    control-plane: policy-controller-webhook
  annotations:
spec:
  minAvailable: 1
  maxUnavailable: 
  selector:
    matchLabels:
      app.kubernetes.io/name: policy-controller
      app.kubernetes.io/instance: policy-controller
      control-plane: policy-controller-webhook
...

new.yaml:

...
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: policy-controller-webhook
  labels:
    helm.sh/chart: policy-controller-0.7.0
    app.kubernetes.io/name: policy-controller
    app.kubernetes.io/instance: policy-controller
    app.kubernetes.io/version: "0.8.2"
    app.kubernetes.io/managed-by: Helm
    control-plane: policy-controller-webhook
spec:
  minAvailable: 1
  selector:
    matchLabels:
      app.kubernetes.io/name: policy-controller
      app.kubernetes.io/instance: policy-controller
      control-plane: policy-controller-webhook
...

Output:

metadata  (document #6)
  - one map entry removed:
    annotations:

spec  (document #6)
  - one map entry removed:
    maxUnavailable:

metadata  (document #8)
  - one map entry removed:
    annotations:

metadata  (document #19)
  - one map entry removed:
    annotations:

metadata  (document #20)
  - one map entry removed:
    annotations:

spec.template.spec.containers.policy-controller-webhook  (document #21)
  - one map entry removed:
    args:

Checklist

• Chart version bumped in Chart.yaml according to semver. Where applicable, update and bump the versions in any associated umbrella chart
• Variables are documented in the values.yaml and added to the README.md. The helm-docs utility can be used to generate the necessary content. Use helm-docs --dry-run to preview the content.
• JSON Schema generated.
• List tests pass for Chart using the Chart Testing tool and the ct lint command.